E P Forum QRA Data Directory

E&P Forum Quantitative Risk Assessment Data Directory Report No 11.8/250 1996

Introduction

E&P Forum QRA Datasheet Directory

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INTRODUCTION

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The E&P Forum’s “Guidelines for the Development and Application of Health, Safety and Environmental Management Systems” (HSEMS) [1], identifies “Evaluation and Risk Management” as a key element of an HSE management system. The use of formal risk assessment in achieving the goal-setting objectives of this element is becoming widely accepted in E&P companies and an essential framework in recent legislative acts. Experience shows that the application of risk assessment is important to both improved plant and system integrity and cost effectiveness by providing valuable information for risk management decision-making. Formal risk assessment is a structured, systematic process which supplements traditional design and risk management processes. It can be based on qualitative or quantitative methods or a combination, thereof. The objective of formal risk assessment is to analyze and evaluate risk. Risk assessment is made up of three fundamental steps: hazard identification to identify what could go wrong, consequence assessment to address the potential effects and frequency assessment to determine the underlying causes and likelihood or probability of occurrence of the hazardous event. In risk assessment, frequency is estimated based on knowledge and expert judgment, historical experience, and analytical methods combined together to support judgments made by risk assessment teams. Historical experience is expressed in terms of statistical data gathered from existing operations, generally in the form of incidents, base failure rates and failure probabilities. A key issue when using risk assessment is the uncertainties associated with the results and hence, the confidence with which the information can be used to influence decisions. Therein lies the need for reliable data to support E&P risk assessment work. Since incident data are important to providing insight into incident scenarios, the availability of suitable data is a key need of all E&P companies using HSE management systems, regardless of whether the company performs qualitative or quantitative risk assessments. Given the common E&P company need and relatively large resource requirement for data collection and assessment, the E&P Forum formed the QRA Subcommittee in 1989. One of its first project’s was to produce a position paper on Quantitative Risk Assessment [2]. Upon completion of this work, the need for better data to support E&P risk assessments was determined to be a primary work objective of the QRA subcommittee. Activities of the QRA subcommittee include: Workshop on Data in Oil and Gas Quantitative Risk Assessments [3], the Hydrocarbon Leak and Ignition Project (HCLIP) [4] and, most recently, the Risk Assessment Data Directory. Risk Assessment Data Directory The objective of the Risk Assessment Data Directory is to provide a catalogue of information that can be used to improve the quality and consistency of risk assessments with readily available benchmark data and references for common incidents analyzed in upstream production operations. Typical incidents analyzed in E&P risk assessments were identified and divided into four major categories for which twenty six individual datasheets were developed. Each datasheet contains: information describing the event; incident frequency, population and causal data; and a discussion of the data sources, range, availability and application. The directory is intended to be a reference document for estimating screening level and order of magnitude incident frequencies. The directory also provides reference lists of data sources that can be called upon for more detailed information. Its primary applications are for reviewing risk assessments performed by others (e.g., consultants, design contractors, etc.) and evaluating risk in Quantified Risk Assessments (QRAs) and qualitative assessments. As 13/06/2003

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such, the directory is not intended to be a comprehensive catalogue of incident data. Applications requiring more comprehensive data should refer to the original references as well as other publicly available information and company data sources that may be available. The project was carried out as a Subcommittee activity to take advantage of the pooling of knowledge and expertise between participants representing various major E&P companies and other E&P Forum members. Sources for the data include information available to the public and industry such as may be obtained from industry projects and the literature. That is, the directory contains organized publicly available information and data contributed by individual companies which has been previously submitted by other venues. While every reasonable effort has been made to ensure the quality and accuracy of the information and data provided, it is the responsibility of each company or organization using the data to review the information and assure themselves that the data is suitable for their specific application. Development Process The approach for developing the directory was to prepare the data sheets as a QRA Subcommittee activity without any central funding of external consultants. The Shell document, “Guidelines for Risk Assessment Data” developed by SIEP’s E&P HSE Department in 1992 [5] was made available to all members on a confidential basis and acted as the foundation for this new directory. First, the QRA Subcommittee developed a prioritized list of datasheets, generated a data index, and prepared a pro-forma for the contents and organization. Next, a member of the QRA Subcommittee was designated the focal point for each datasheet. The focal points were responsible for coordinating the development of their assigned datasheet. The focal points called on expertise within their own organizations and, in some cases, employed the assistance of various outside consultants. Other QRA Subcommittee members contributed data and reviewed draft data sheets. QRA Subcommittee meetings were held quarterly to peer review and finalize the draft datasheets. This process commenced in November 1994. The final draft datasheets were completed and the draft directory was assembled in second quarter of 1996. As a quality assurance check, the draft directory was then reviewed by an independent expert, and after approval from the E&P Forum Safety, Health and Personnel Competence (SHAPC) committee was issued in fourth quarter of 1996. As with all E&P Forum documents, the directory is available to the public at no charge.

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Directory Scope and Content The directory covers both onshore and offshore E&P activities. The data have been collated under four major categories: Accident Data:

Collated statistical data of accidents (i.e., events that have led to detrimental effects in terms of loss of life, environmental damage or property damage)

Event Data:

Collated statistical data of hazardous events (i.e., events that led to or had the potential to lead to an accident)

Safety Systems:

Collated statistical data on the effectiveness of various safety systems employed to prevent and/or mitigate hazardous events.

Vulnerabilities:

Criteria for assessing the vulnerability of plant and humans to hazardous events.

Under each category, a series of individual data sheets are presented. Human factors have been organized into four datasheets to address the human factors contribution to each category. A total of twenty four datasheets were developed as listed below: Accident Data:

Major Accidents Work-related Accidents Land Transport Air Transport Water Transport Construction Accidents

Event Data:

Process Releases Risers and Pipelines Storage Tanks Blowouts Mechanical Lifting Failures Collisions Human Factors in the Calculation of Loss of Containment Frequencies

Safety Systems:

Fire & Gas Detection ESD & Blowdown Emergency Systems Blowout Prevention Active Fire Protection Human Factors in the Determination of Event Outcomes

Vulnerabilities:

Vulnerability of Humans Vulnerability of Plants Escape, Evacuation and Rescue Human Factors in the Assessment of Fatalities during Escape and Sheltering Human Factors in the Assessment of Fatalities during Evacuation and Rescue

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The basic content of each data sheet is as follows: Scope:

Brief outline of data presented in datasheet.

Application:

Details of the situation for which the datasheet would be applicable including statements regarding where care should be exercised in its use.

Key Data:

Data presented in a tabular and/or graphical format. Discussion covering data source, data range, availability, strengths and limitations, applicability, estimating frequencies.

Ongoing Research:

Ongoing work which may be used later to update datasheet.

References:

Detailed list of references.

Note that the format presented above is general, individual datasheets vary to some extent, depending on relevance and availability of information. The objective has been to identify as far as practical data available in the public domain and to discuss its applicability. However in a few isolated cases, reference is made to data held by an E&P Forum member that is not available publicly. Where this is the case the judgment of the QRA Subcommittee is that this data is sufficiently robust to include even though the user is not able to source the data directly. It is not the intention of the Directory to in any way address or comment on the best approach or methods for risk assessment studies. In some of the data sheets, particularly for Safety Systems, the key data presented is in terms of how ‘reliable’ these systems are. “Reliability Analysis” is a distinct specialist area. Any detailed assessment would require expert assistance. Another area that is recognized as directly influencing the frequency of accidents and events is “Human Factors.” Again, this is a distinct specialist area which would require expert assistance if any detailed assessment work was to be undertaken. “Human Factor” data sheets have been included within the “Event Data,” “Safety Systems” and “Vulnerabilities” categories. It should also be noted that there are many other areas where expert assistance would be needed to undertake an in-depth study, e.g., assessing structural vulnerabilities, marine hazards. Directory Application The intention is that this document may facilitate the systematic assessment of risks within individual E&P Forum member companies and across the E&P industry. It is hoped that the directory will be a valuable reference document. Examples of specific applications of the directory include: • • • • •

Estimating screening level and order of magnitude incident frequencies Reviewing external risk assessment (e.g. those performed by consultants, design contractors, etc.) Evaluating risk in QRAs and qualitative assessments Comparing industry and corporate performance Identifying important risk contributors

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Updating Plans It is recognized and accepted that the data presented in the “E&P Forum Risk Assessment Data Directory” will become out of date. Nevertheless, many of the data bases identified are actively maintained and; hence, by directly accessing these source databases, up-to-date information can be obtained. In the future, this directory may be updated. The E&P Forum will maintain a file for each data sheet. There is an open invitation to forward any new or better information, or data from other geographic areas, to the E&P Forum. It would also be appreciated if the E&P Forum could be notified of any errors identified. This information will be periodically reviewed by the QRA Subcommittee.

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REFERENCES 1. E&P Forum, “Guidelines for the Development and Application of Health, Safety and Environmental Management Systems”, Report No. 6.36/210, July 1994. 2. E&P Forum, “Quantitative Risk Assessment, A Position Paper Issued by the E&P Forum”, Report No. 11.2/150, May 1989. 3. E&P Forum, “Workshop on Data in Oil and Gas Quantitative Risk Assessments”, Report No. 11.7/205, January 1994. 4. E&P Forum, “Hydrocarbon Leak and Ignition Database”, DNV Technica, March 1992. 5. Shell Internationale Petroleum Maatschappij B. V., “Guidelines for Risk Assessment Data”, May 1992.

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Major Accidents

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MAJOR ACCIDENTS

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TABLE OF CONTENTS

1. SUMMARY--------------------------------------------------------------------------------------------- 3 2. MAJOR OFFSHORE ACCIDENTS INVOLVING FATALITIES -------------------------- 3 3. MAJOR ONSHORE ACCIDENTS WITH HIGH PROPERTY DAMAGE LOSSES- 3 4. MAJOR OFFSHORE ENVIRONMENTAL ACCIDENTS---------------------------------- 4 REFERENCES----------------------------------------------------------------------------------------- 16

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SUMMARY

This datasheet provides a summary of major offshore and onshore accidents over the past 20-25 years. The offshore accidents pertain to the upstream oil and gas production industry; the onshore accidents involve the petrochemical industry. The offshore accidents are analyzed based on the fatalities involved, whereas the onshore accidents are based on the property damage losses involved. In addition, this datasheet also lists the most severe offshore environmental accidents associated with platform spills, blowouts, and tanker spills. For all the different major accident analyses (whether based on fatalities, property damage, or environmental damage) this datasheet provides a list of the worst accidents involved and subsequently provides an analysis of all the accidents in that accident category using bar diagrams.

2.

MAJOR OFFSHORE ACCIDENTS INVOLVING FATALITIES

The Worldwide Offshore Accident Databank (WOAD) project was launched in 1983 and at present includes accident data from 1970 and onwards [1]. This database is maintained by DNV Technica, which collects data on major offshore accidents from public sources worldwide. Although the database attempts to cover worldwide accidents, there are areas of the world for which limited information is available, e.g. countries with a fully state-owned offshore industry. For such areas only accidents to units owned by private, foreign operators is normally known. Further, although WOAD includes accidents in the US Gulf of Mexico, a more detailed listing of these accidents is maintained by the US Minerals Management Service (MMS). Therefore, the WOAD analysis in this section pertaining to US Gulf of Mexico has been updated with MMS data [3]. The WOAD database [1] was searched for all accidents involving fatalities. The period covered was 1970 through June 1995, in which there were a total of 446 accidents. The total number of fatalities involved was 1893. Table 2.1 lists all accidents with 10 or more fatalities along with the operating mode, the main event that caused the accident, the extent of damage involved, and the geographic area where the platform was operating. Table 2.2 breaks down the fatalities by the type of unit involved. Table 2.3 provides a breakdown of fatalities by 5Year periods, whereas Table 2.4 provides a breakdown of fatalities by geographic area.

3.

MAJOR ONSHORE ACCIDENTS WITH HIGH PROPERTY DAMAGE LOSSES

Tables 3.1 and 3.2 list the worst property damage losses for onshore accidents in the hydrocarbon-chemical industry. These data were obtained from Marsh & McLennan Protection Consultants [2], who maintain information on the top 100 industrial property damage losses [5] but do not provide information on any fatalities or injuries involved.

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MAJOR OFFSHORE ENVIRONMENTAL ACCIDENTS

Tables 4.1 through 4.5 provide information on the major offshore environmental accidents involving platform spills, blowout spills and major tanker spills. Information pertaining to platform and blowout spills was obtained from [3] and applies only to the US Gulf of Mexico. Tables 4.4, 4.5 and 4.6 data from [4] pertain to tanker spills on a worldwide basis. Table 4.7 provides a comparison between the various environmental spills for the three 5-year periods between 1976 and 1990 for the US. The data were obtained [3] & [4]. The data show that the bulk of the volume in offshore spills came from tankers. The following abbreviations for geographical areas are used in the tables: US GOM Europe NS

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= =

US Gulf of Mexico Europe North Sea

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Table 2.1: Top Offshore Incidents Listed in Decreasing Order of Fatalities Involved (Worldwide, 1970 - 1995) ([1]: WOAD ‘95, DNV Technica)

Date(yr/mo/da) 88/07/06 80/03/27 89/11/03 82/02/15 83/10/25 79/11/25 86/11/06 84/08/16 91/08/15 80/10/02 74/10/09 78/06/26 77/12/08 77/12/08 71/10/13 78/06/03 87/12/21 87/12/21 82/11/17 85/10/17 80/03/20 90/11/25 83/03/20 81/08/13 82/04/30 76/04/16 77/11/23 89/10/03 80/06/04 85/05/20 72/05/29 92/03/14 89/05/05 95/01/18 89/07/31 82/05/27 90/12/06 85/11/04

Type of Unit Jacket Semi-Sub Drill Ship Semi-Sub Drill Ship Jackup Helicopter Jacket Lay Barge Jackup Jackup Helicopter Helicopter Jacket Drill Barge Helicopter Helicopter Jackup Helicopter Mobile Helicopter Helicopter Barge Helicopter Helicopter Jackup Helicopter Pipeline Helicopter Drill Barge Helicopter Helicopter Helicopter Jacket Barge Helicopter Helicopter Barge

Oper. Mode Production Accomodation Expl. Drill Expl. Drill Drilling Transfer, Wet Other Develop. Drill Construct. Expl. Drill Drilling Other Other Production Expl. Drill Other Other Stacked Other Construct. Other Other Construct. Other Other Transfer, Wet Other Production Other Transfer, Wet Other Other Other Repair Transfer, Wet Other Other Construct.

Damage Total Loss Total Loss Severe Total Loss Total Loss Total Loss Total Loss Significant Total Loss Minor Severe Total Loss Total Loss Minor Severe Total Loss Total Loss Minor Total Loss Severe Total Loss Total Loss Severe Total Loss Total Loss Total Loss Total Loss Significant Total Loss Severe Total Loss Total Loss Total Loss Severe Total Loss Total Loss Total Loss Total Loss

Main Event Fire Capsizing Capsizing Capsizing Capsizing Capsizing Other Fire Capsizing Blowout Capsizing Other Collision Helicopter Fire Other Collision Helicopter Other Explosion Other Other Fire Other Other Capsizing Other Fire Other Capsizing Other Other Other Explosion Capsizing Other Other Capsizing

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Fatalities1 167 123 91 84 81 72 45 42 22 19 18 18 17 17 16 15 15 15 15 14 14 13 13 13 13 13 12 11 11 11 11 11 10 10 10 10 10 10

Injuries1 60 NA 0 0 0 0 2 19 NA 19 0 0 1 0 0 0 0 0 0 0 0 0 32 0 0 0 0 4 0 0 NA 1 0 NA 0 0 2 0

Area Europe NS Europe NS Asia South America NE Asia East Asia East Europe NS America SE Asia East Middle East Middle East Europe NS US GOM US GOM America SW Middle East US GOM US GOM Asia East Central America America SE Europe East Africa West Europe NS Asia South US GOM Europe NS US GOM Africa West US GOM US GOM Europe NS Asia East Africa West US GOM Asia South Asia South Europe NS

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Table 2.2: Breakdown of Incidents and Fatalities by Type of Unit (Worldwide, 1970-June 95) [1]) Type of Unit

AI BA BO CO

DB

DS

FI

FL

1

42

72

124

6

2

% of Total Units

0

1

1

10

2

4

0

0

5

34

5

1

6

11

47

1

0

77

No. of Units

1

26 303

HE

JT

JU

LB

MO PI RI

SC

SH

SS

SU TE TL WS OT Totals

150 975 515

33

28

3

8

429

24 10 18

18

1

1

2

0

0

0

15

1

0

187

48

4

6

3

0

0

12

27

3

42

63 0

70

2

2904

1

2

0

100

3

1

3

1

446

No. of Fatal Incidents

0

% of Total Fat. Incidents

0

1

0

1

2

11

0

0

17

11

1

1

1

0

0

3

6

1

1

0

1

0

100

Total Fatalities

0

35

6

16

55

236

2

0

450 504 231

28

21

14 0

0

17

255

3

14

1

4

1

1893

% of Total Fatalities

0

2

0

1

3

12

0

0

24

1

1

1

0

1

13

0

1

0

0

0

100

27

12

0

Note 1: Since WOAD is an incident database only (i.e., it does not provide unit operating years), the numbers in this row represent the frequency of the unit in the incident database.

SC

Subsea install./complet.

SH

Ship: e.g., FSU, FPSO

SS

Semi-submersible

SU

Submersible

TE

Drilling tender

TL

Tension leg platform

WS

Well support structure

OT

Other

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10 0 OT

Platform rig

WS

Pipeline

RI

TL

PI

20

TE

Mobile unit (not drilling)

SU

MO

SS

Lay barge

SH

Jackup

LB

SC

Jacket

JU

RI

JT

30

PI

Helicopter-Offshore duty

MO

HE

LB

Flare

JU

FL

40

JT

Other/Unkn. fixed structure

HE

Drill ship

FI

FL

Drill barge

DS

FI

Concrete structure

DB

DS

Loading buoy

CO

DB

BO

Breakdownof Number of FatalitiesandNumber of IncidentsbyType of Unit (Worldwide, 1970- June 95)

CO

Barge (not drilling)

BO

BA

BA

Artificial Island

AI

Type of Unit

AI

Percent

Code

Type of Unit %of Total Incidents %of Total Fatalities

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Table 2.3: Breakdown of Fatalities by 5-Year Periods (Worldwide, 1970 - June 95) [1]) 5-Year Period

1970-75

1976-80

1981-85

1986-90

1991-95

No. of Incidents

95

111

115

86

39

1

Total 446

% of Total Incidents

21

25

26

19

8.7

100

Total Fatalities

190

348

650

591

114

1893

34

31

6

100

10 18 % of Total Fatalities Note 1: For 1995 data was available only up to June 1995.

Breakdown of Number of Fatalitiesand Number of Incidentsin 5-Year Periods (Worldwide, 1970 - June 1995) 35 30

Percent

25 20 15 10 5 0 1970-75

1976-80

1981-85

1986-90

1991- June 95

5-Year Period % of Total Incidents

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%of Total Fatalities

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Table 2.4: Breakdown of Fatalities by Geographic Area (Worldwide, 1970 - June 95) [1]) 1

Geographic Area No. of Incidents % of Total Incidents Total Fatalities

% of Total Fatalities

US GOM 297 67 570 30

Europe N.S. 58 13 511 27

Asia 27 6.1 373 20

Australia 5 1.121 10 0.528

Other 59 13.2 429 22.7

Totals 446 100 1893 100

Bre a kdow n of Num be r of Incide nts a nd Num be r of Fa ta litie s by Are a (W orldw ide , 1970 - June 95) 70 60

Percent

50 40 30 20 10 0 US GOM

Europe NS

A sia

A ustralia

Other

Ar e a % of Total Incidents

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% of Total Fatalities

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Table 3.1: Top Property Damage Losses in the Hydrocarbon-Chemical Industry [2] [5]) Date

Name of Unit

Type of Unit

Operating Mode

Main Event

Cost (106 US $)a

Area

PETROCHEM

OPERATING

EXPLOSION

675 / 716

America South West

REFINERY

OPERATING

FIRE

300 / 327

America South East

PETROCHEM

OPERATING

FIRE/

215 / 243

America South West

REFINERY

OPERATING

FIRE

190 / 192

Europe West

89/10/23

High Density Polyethylene Reactor

88/05/05

Depropanizer Column

87/11/14

Treating Section-Gas Processing

92/11/09

Fluidized Catalytic Cracking Unit

92/10/16

Hydrodesulfurization Unit

REFINERY

STARTUP

FIRE

161 / 162

Asia East

74/06/01

Cyclohexane Oxidation Reactor

PETROCHEM

OPERATING

FIRE

66 / 161

Europe West

91/03/11

Chlorine Unit-VCM Plant

PETROCHEM

OPERATING

EXPLOSION

150 / 153

Central America West

84/07/23

Monoethanolamine Absorber Column

REFINERY

OPERATING

FIRE

127 / 152

America North East

77/04/03

Refrigerated Propane Storage

GAS PROCESSING

OPERATING

FIRE

76 / 149

Middle East

81/08/21

Naphtha Storage Tanks

REFINERY

STORAGE

FIRE

100 / 141

Middle East

68/01/20

Slop Tank

REFINERY

OPERATING

FIRE

28 / 117

Europe West

79/09/01

Ethanol Storage Tank/DWT Tanker

REFINERY

TRANSFER

EXPLOSION

68 / 114

America South West

64/06/14

Crude/Product Storage

REFINERY

STORAGE

FIRE

22 / 111

Asia East

91/05/01

Nitroparaffin Unit

PETROCHEM

OPERATING

EXPLOSION

105 / 107

America South East

77/05/11

Crude Oil Pipeline

GAS PROCESSING

TRANSFER

FIRE

55 / 106

Asia East

89/04/10

Hydrocracker Unit

REFINERY

OPERATING

FIRE

95 / 101

America North West

EXPLOSION

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Table 3.1 (continued): Top Property Damage Losses in the Hydrocarbon-Chemical Industry [2] [5])

Name of Unit

Type of Unit

Operating Mode

Main Event

Cost (106 US $)a

Area

78/05/30

Alkylation Tank Farm

REFINERY

STORAGE

FIRE

55 / 100

America South West

78/04/15

Gas Transmission Pipeline

GAS PROCESSING

TRANSFER

EXPLOSION

54 / 97

Middle East

70/12/05

Hydrocracking Unit

REFINERY

OPERATING

EXPLOSION

27 / 95

America North East

84/08/15

Fluid Bed Coking Unit

REFINERY

OPERATING

FIRE

76 / 91

Canada

87/03/22

Hydrocracking Unit

REFINERY

STARTUP

FIRE

79 / 89

Europe West

66/01/04

Butane Sphere

REFINERY

STORAGE

FIRE

18 / 84

Europe West

91/03/12

Ethylene Oxide Unit

PETROCHEM

OPERATING

EXPLOSION

80 / 82

America South West

89/03/07

Aldehyde Column

PETROCHEM

OPERATING

EXPLOSION

77 / 82

Europe West

85/05/19

Ethylene Plant

PETROCHEM

OPERATING

FIRE

65 / 77

Europe South, Mediterranean

77/07/08

Pipeline

PIPELINE

STARTUP

FIRE

40 / 77

Arctic, America

67/08/08

Isobutane Pipeline

REFINERY

TRANSFER

FIRE

17 / 77

America South East

Date

a

Two cost figures are listed: the first figure is the accident cost at the time the accident occurred. The second figure is the trended accident cost in 1993 dollars.

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Table 3.2: Summary of Top 100 Major Onshore Incidents (1963-1993) [2]) Industry

Total US $ Loss (106)* 2,899

Percent of Total US $ 45

No. of Incidents

Percent of Incidents

44

44

Petrochemical

2,391

37

36

36

Gas Processing

621

10

8

8

Terminal

243

4

7

7

Miscellaneous

249

4

5

5

Refining

*

Based on 1993 US dollars.

Summary of Top 100 Major Onshore Incidents(1963-1993)

Percent

60 40 20 0 Refining

Petrochemical

Gas Processing

Terminal

Miscellaneous

Industry Type %of Total Property Damage %of Total Number of Accidents

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Table 4.1: Large Spills (> 1000 BBL) from Platforms in the Gulf of Mexico (1970-1990) [3] Date 70/12/01 70/10/02 74/04/17 88/02/07 90/01/24 70/01/09 73/01/26 81/12/11 73/05/12 90/05/06 76/12/18 74/09/11 79/11/24 80/11/14

Spill Size 53,000 30,000 19,833 15,576 14,423 9,935 7,000 5,100 5,000 4,569 4,000 3,500 1,500 1,456

Material Oil Oil Oil Oil Condensate Oil Oil Oil Oil Oil Oil Oil Diesel Oil

Table 4.2: Large GOM Spill (>1000 bbl) Statistics (1970-1990) [3]) Material Number of Small Spills Amount Spilled (bbl)

Oil 12 158,969

Diesel 1 1,500

Condensate 1 14,423

Total 14 174,892

Large GOM Spill (>1000 bbl) Statistics (1970-1990) 100

Percent

80 60 40 20 0 Oil

Diesel

Condensate

Material Spilled % of Total Number of Spills

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% of Total Volume of Spills

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Table 4.3: Blowout Spills in the Gulf of Mexico (1970-1990) [3]) Date

Spill Size (BBL)

Material

70/12/01

53,000

Oil

70/02/10

30,000

Oil

71/10/16

450

Oil

74/12/22

200

Oil

74/09/07

75

Oil

81/11/28

64

Oil

87/03/20

60

Condensate

85/02/23

40

Oil

90/05/30

12

Oil/Mud

90/09/09

8

Condensate

Table 4.4: GOM Blowout Spill Statistics (1970-1990) [3] Material Number of Small Spills Amount Spilled (bbl)

Oil 8 83,841

Condensate 2 68

No Reportable Spill 136 0

Total 146 83,909

Percent

GOM Blowout Spill Statistics (1970-1990) 100 50 0 Oil

Condensate

No Reportable Spill

Material % of Total Number of Blowouts

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% of Total Volume of Blowout Spill

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Table 4.5: Major Tanker Spills Worldwide (1974-1992) [3]) Date 83/08/05 78/03/16 79/07/19 79/08/02 88/11/10 77/02/23 79/11/15 76/05/12 80/02/23 89/12/19 92/12/03 85/12/06 75/05/13 92/04/17 74/11/09 83/01/07 78/12/31 75/01/10 74/08/09 83/12/10 78/12/07 75/01/29

Spill Location/Marsden Sq. 75km NW of Cape Town/442 Off Portsall, Brittany NW France/145 30km NE of Trinidad Tobago/43 450km East of Barbados/42 800 Mi. NE St. Johns, Newfoundland/185 320 Mi. W of Kauai Island/89 Bosporus Strait/178 North Coast of Spain/145 Off Pilos, Greece/142 Atlantic, 100 Mi. from Morocco/109 Port of La Coruna Spain/145 Arabian Gulf/103 Caribbean Sea 60 Mi. NW of Puerto Rico/43 Maputo Bay, Mozambique/404 Tokyo Bay/131 58 Mi. from Muscat, Oman/103 Bay of Biscay, Spain/145 180 Mi. W of Iwo Jima/95 Magellan Strait, Chile/486 Arabian Gulf/103 Strait of Malacca, Indonesia/26 Port Leixoes, Portugal/145

Spill Size (bbls) 1,760,000 1,628,000 1,016,761 987,714 952,900 742,000 696,000 670,000 600,000 560,000 521,429 500,000 420,000 380,952 375,000 370,000 350,000 337,000 330,000 324,000 314,142 300,000

Material Arabian Crude Lt. Arabian Crude Arabian Crude Arabian Crude North Sea Crude Indonesian Crude Libyan Crude Kuwait Crude Libyan Crude Iranian Lt. Crude Brent Lt. Crude Iranian Lt. Crude Venezuela Crude Heavy #6 Fuel Oil Naphtha Iranian Crude Iranian Crude Crude Lt. Arabian Crude Lt. Arabian Crude Crude Iranian Crude

Table 4.6: Worldwide Tanker Spill Statistics (1974-1992) [3]) Spill Size (BBL)

Number

1000-14,999 15,000-49,999 50,000-199,999 200,000+

108 38 33 34

Totals

213

Total Volume Spilled (BBLs) 566,500 1,024,000 3,548,500 16,789,500 21,928,500

Worldwide Tanker Spill Statistics (1974-1992)

Percent

80 60 40 20 0 1000-14,999

15,000-49,999

50,000-199,999

200,000+

Individual Spill Size (bbl) % of Total Number of Spills

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% of Total Volume Spilled

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Table 4.7: Comparison of Spills During 5-Year Periods [3] [4]) 5-Year Period

1976-80 1981-85 1986-90 Number of Volume of Number of Volume of Number of Volume of Spill Category Spills Spills (bbl) Spills Spills Spills Spills Small GOM Spill 21 4243 27 4747 9.0 1073.0 % of Total 22.83 1 28.7 2.5 13.8 0.2 3 6956 1.0 5100.0 3.0 34568.0 Large GOM Spill % of Total 3.26 1 1.1 2.7 4.6 7.2 Blowouts GOM** 40 0 44.0 104.0 33.0 80.0 % of Total 43.48 0 46.8 0.1 50.8 0.0 Tanker Spills US 28 770000 22.0 180000.0 20.0 445000.0 % of Total 30.43 99 23.4 94.8 30.8 92.6 Total 92 781199 94 189951 65 480721 **

Blowouts that have oil releases are also counted in the small or large spill results.

Comparison of US Spills During 5-Year Periods 100.00 80.00 60.00 40.00

Percent 20.00 0.00 # of Spills

Vol. of Spills

1976-80

Small Platform Spills in US GOM

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# of Spills

Vol. of Spills

# of Spills

1981-85 5-Year Periods Large Platform Spills in US GOM

Blowout Spills in US GOM

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1986-90 Tanker Spills in US Waters

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REFERENCES

1. WOAD - Worldwide Offshore Accident Databank Version 4.10 - DNV Technica 2. A. Manuele, “One Hundred Largest Losses - A Thirty Year Review of Property Damage Losses in the Hydrocarbon - Chemical Industries”, Marsh & McLennan Protection Consultants, April 1986. 3. “Accidents Associated with Oil and Gas Operations”, OCS 1956-1990, OCS MMS 920058, October 1992, U.S. Minerals Management Services, Department of Interior. 4. Worldwide Tanker Spill Database, US Mineral Management Services, US Department of Interior. 5. D. Mahoney, “Large Property Damage Losses in the Hydrocarbon - Chemical Industries.” A Thirty-year Review, Sixteenth Edition, Marsh & McLennan Protection Consultants, 1995

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WORK RELATED ACCIDENTS

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TABLE OF CONTENTS

1. WORK RELATED FATAL ACCIDENT RATES 1.1 SUMMARY------------------------------------------------------------------------------------------- 3 1.1.1 Scope -------------------------------------------------------------------------------------------------------------------3 1.1.2 Application------------------------------------------------------------------------------------------------------------3

1.2 KEY DATA ------------------------------------------------------------------------------------------- 3

2. WORK RELATED LOST TIME ACCIDENT RATES 2.1 SUMMARY----------------------------------------------------------------------------------------- 10 2.1.1 Scope ----------------------------------------------------------------------------------------------------------------- 10 2.1.2 Application---------------------------------------------------------------------------------------------------------- 10

2.2 KEY DATA ----------------------------------------------------------------------------------------- 10 REFERENCES----------------------------------------------------------------------------------------- 14

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1.

WORK RELATED FATAL ACCIDENT RATES

1.1

SUMMARY

1.1.1

Scope

Rev 0

This datasheet provides data on work related Fatal Accident Rates (FAR’s) that arise in the Exploration and Production Industry. The data are subdivided to provide guidance on typical FAR’s that are experienced by activity, offshore, onshore, and by region. Where data are available from more than one source, multiple tables are included. Although transport and fire/explosion induced fatalities are not technically work related, they have been included for information. 1.1.2

Application

The data presented are applicable for work related accidents when undertaking QRA relating to exploration and production. Wherever possible the data selected should be those that most closely resemble the situation being modelled, rather than the more generic type of data given in the first few tables. The original data sources present the data in a variety of different ways - e.g. as FAR’s, per 100,000 workers, per 1000 man years - and these have all been adjusted to Fatality Rate per 108 exposed hours to facilitate comparison and use.

1.2

KEY DATA

Data Tables Table 1: Overall Fatal Accident Rates from Reference 1 FUNCTION Exploration Production Drilling TOTAL

1991

1992

1993

8.1 9.1 13.4 9.6

7.2 10.1 10.8 9.9

5.9 11.1 10.4 10.4

10 YEAR AVERAGE 13.94 10.27 20.46 12.04

Note that in this table the FAR’s for each function are calculated from the fatalities and exposed hours for that function, whilst the total is all fatalities and exposed hours. This explains why the total FAR’s are not the sum of the individual function FAR’s. These data are generic, containing as they do offshore, onshore, Company personnel, Contractor personnel, and regional components. The data are broken down into more specific values in the following tables. The data from years 1991 and 1992 have been included for comparative purposes, and this approach is retained wherever possible. 13/06/2003

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Table 2: Fatal Accident Rates by Accident Type from [1] ACCIDENT TYPE Falls Motor Vehicle Drowning Explosion/Fire Struck by Caught Between Electrocution Helicopters All Others TOTAL

1991

1992

1993

10 year AVERAGE

0.85 1.49 0.85 0.85 1.60 0.21 0.85 1.81 1.06 9.6

0.95 2.33 1.06 1.06 1.38 0.32 0.21 1.38 1.16 9.9

0.87 1.31 2.28 1.74 2.07 0.76 0.65 0.0 0.76 10.4

1.29 1.74 1.39 1.58 1.93 0.47 0.49 1.57 1.56 12.04

Table 3: Fatal Accident Rate by Region from [1] REGION Europe USA Canada South America Africa Middle East Australasia ALL REGIONS

1991 3.2 7.3 3.2 17.8 23.5 10.1 3.9 9.6

1992 8.5 3.4 4.0 15.7 12.3 23.1 5.1 9.9

1993 4.6 4.8 5.2 26.7 12.1 11.8 8.5 10.4

10 year AVERAGE 10.02 5.93 7.81 28.69 18.55 17.01 11.46 12.04

Table 4: FAR’s for 1993 by Region and Location from [1] REGION Europe USA Canada South America Africa Middle East Australasia ALL REGIONS

ONSHORE 2.5 6.0 5.5 27.0 11.1 12.5 5.1 11.2

OFFSHORE 6.2 N/A N/A N/A 21.8 N/A 14.7 8.1

Discussion The data produced by the E&P Forum [1] are probably the most comprehensive in this area as they are developed from returns by over 33 member companies world wide. It should be noted, however, that these returns are voluntary, so that the data may not be as accurate as those presented in references 2 and 3, which use statutory returns as the basis for their results. The wide ranging nature of this data source means that the results presented here may be used with a fair degree of confidence for estimating the risk of fatality from work related accidents. They should not be treated as anything other than generic figures, for indicative use when 13/06/2003

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more detailed risk figures (e.g. risk of fatality from dropped objects) are not available from site specific studies. Table 5: Overall Fatal Accidents from [2] and [3] (UK) FUNCTION Construction(1) Drilling Production Maintenance Diving Helicopters Boats Cranes Domestic(2) Structures(3) Unallocated TOTAL FAR Notes: (1) (2) (3) (*)

1991 0 0 0 0 0 11 1 0 0 0 1 13 15.28

1992 1 1 0 1 0 1 0 1 0 0 0 5 6.61

1993 1 0 0 0 0 0 0 0 0 0 0 1 1.14

10 year AVERAGE 0.3 0.7 0.4(*) 1.7 0.1 1.8 0.6 0.6 0 0 1.2 7.4(*) 9.05(*)

Includes commissioning Includes catering Includes plant and structure modifications Excludes Piper Alpha

Table 6: Fatal Accidents by Accident Type from [2] and [3] (UK) TYPE Fire/Explosion Air Transport Sea Transport Slips/Trips/Fall Falling Objects Handling Goods Crane Ops Use of Machinery Electrical Other TOTAL FAR (*)

1991 0 11 1 0 0 0 0 0 0 1 13 15.28

1992 0 1 0 0 1 2 1 0 0 0 5 6.61

1993 0 0 0 1 0 0 0 0 0 0 1 1.14

10 year AVERAGE 0.4(*) 1.7 0.2 0.5 0.1 0.3 0.2 1 0.1 2.9 7.4(*) 9.05(*)

Excludes Piper Alpha

Note that the values in the table are the number of fatalities - data are not available on the exposed hours for each function, so the individual FAR’s cannot be calculated. If the fatalities from Piper Alpha are included in the 10 year average then the mean FAR rises to 31.29, and the average number of fatalities per year becomes 23.9. Discussion The data presented in tables 5 and 6 have been developed from accident returns made on a statutory basis to the UK regulators. As such they provide accurate FAR data for use in 13/06/2003

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analyses of installations on the UK continental shelf. They are only applicable to offshore operations. The data quoted in the references are based on an exposed population rather than an exposure time. In order to make these data comparable with those from reference 1, therefore, they have been converted to the FAR base of “per 108 exposed hours”. The following assumptions were used in making the conversion: · · ·

A two week on/two week off rota is standard. Exposure time is 14 hours per day. Off duty hours are ‘non-exposed’.

Where work patterns do not fit these assumptions then the figures quoted in the tables should be adjusted accordingly. Table 7: Overall Fatal Accident Rates from [4] (Norway) FUNCTION Drilling Production TOTAL

1991 0 0 0

1992 0 0 0

1993 6.75 6.75 13.51

10 year AVERAGE N/A N/A 2.69

Discussion These data are obtained from the Norwegian Petroleum Directorate Annual Report, and are, therefore, only applicable to operations in the Norwegian sector. The FAR values in table 7 are based on the total number of exposed hours in the Norwegian sector. A more detailed analysis shows that the number of production hours exceeds significantly those of drilling. Using the function specific values generates the values given in table 8. Table 8: Function Specific Fatal Accident Rates from [4] (Norway) FUNCTION Drilling Production TOTAL

1991 0 0 0

1992 0 0 0

1993 47.56 7.87 13.51

10 year AVERAGE N/A N/A 2.69

The data are reported on a “per 1000 man years” basis, and have been converted to 108 exposed hours by making the following assumptions: • • •

A two week on/two week off rota is standard. Exposure time is 14 hours per day. Off duty hours are ‘non-exposed’.

Where work patterns do not fit these assumptions then the figures quoted in the tables should be adjusted accordingly.

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Table 9: Fatal Accidents from [5] (Alberta Occupational Health & Safety) TYPE Worksite Highway Disease TOTAL FAR

1989 3 2 0 5 4.1

1990 3 11 0 14 11.35

1991 7 1 1 9 7.36

10 year AVERAGE 8.1 5.1 1 14.2 10.71

Discussion The data presented in table 9 are valid for onshore exploration and production in Alberta. The statistics are not comprehensive so it is not possible to develop the FAR’s for the various categories. The values in the table are numbers of fatalities, whilst the FAR is the overall fatal accident rate for that year. The base exposure hour data are presented as man years, with the qualification that 100 man years is equivalent to 200,000 man hours. This implies an average exposure time of 2,000 hours each year. These data are probably not particularly useful for use in QRA, except at a coarse level. Should analysts be interested in more detailed fatality frequencies for this part of the world then they should contact Alberta Occupational Health and Safety, whose address is in the reference. Table 10: Overall Fatal Accident Rates from [6] (Vessels, UK Sector) TYPE Merchant Vessels FAR

1990 5 10.3

1991 9 19.3

1992 4 9.9

1993 3 6.0

AVERAGE 5.25 11.4

Discussion The data presented in table 10 are for merchant vessel seamen on UK registered vessels only, and excludes fishermen. These figures are not rigorous, and should only be used for coarse estimates and comparisons. In [7] the overall FAR for merchant seamen on UK registered vessels is given as 9. Estimating Frequencies The data presented in the tables above may be used for one of two objectives: ·

To enable a Company to compare its risk figures for a specific site with typical values achieved by the Exploration and Production Industry as a whole.

·

Estimating the frequency of fatalities resulting from work related accidents. Their use in this area should be as a first pass only, unless more detailed work is intractable. It will have been noted that - especially in sector specific reports such as [2], [3], and [4] 13/06/2003

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- the FAR values vary significantly from one year to the next, and this severely limits their use as a definitive tool. The following short example (using imaginary numbers) demonstrates how to use FAR’s to estimate a fatality frequency: There is a particular work activity that exposes 2 personnel to risk for 6 hours a day for 50% of the year, and has a historical FAR of 5. The number of exposed hours

= 2 men x 6 hrs x 182 days = 2,184 hours per year.

The risk of fatality is the exposed hours multiplied by the FAR (fatalities per 108 exposed hours). Thus the risk of fatality = 2,184 x (5/108) per year = 1.1 x 10-4 per year. It should be stressed that although there are some fatality rates for explosions and burns included, such events are normally considered as major hazards and should, therefore, be subjected to detailed and site specific analysis. Comparative Statistics Tables 11 and 12 below, contains a listing of FAR’s from other UK industries, to enable comparisons to be drawn between the fatality rates for the Exploration and Production sector and other types of industry. The values presented are developed from statistics published by the Royal Society for the Prevention of Accidents. Table 11: Fatal Accident Rates for Employees in Selected Onshore Industries INDUSTRY Agriculture1 Energy & Water2 Manufacturing Construction Service Industries All Industries

1991 4.78 3.24 0.96 4.95 0.37 0.90

1992 3.56 3.94 0.80 4.68 0.32 0.75

1993 4.36 3.03 0.80 4.26 0.37 0.69

(1) Includes forestry and fishing, but excludes sea fishing. (2) Includes offshore fatalities from the UKCS.

Table 12: Fatal Accident Rates for Self-Employed in Selected Onshore Industries INDUSTRY Agriculture1 Energy & Water2 Manufacturing Construction Service Industries All Industries

1991 5.80 N/A 1.97 2.07 0.59 1.44

1992 6.91 N/A 1.49 1.33 0.37 1.22

1993 3.67 N/A 0.48 2.13 0.43 1.06

(1) Includes forestry and fishing, but excludes sea fishing. (2) Includes offshore fatalities from the UKCS.

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These data are presented on a “per 100,000” basis, and have been converted to FAR’s using the following assumptions: · 8 hours exposure per day. · 5 days exposure per week. · 20 days holiday per worker, and 8 statutory holiday days per year. This results in a exposure time of 1,880 hours per worker per year. If appropriate the values in the table should be adjusted when used for comparative purposes. Ongoing Research Although the term research is not particularly appropriate, it is fair to say that fatality statistics are collected and published on an ongoing, annual, basis. It is entirely possible, therefore, to track the performance of the industry, or a particular sector within it, to assess and analyse the trends in safety performance.

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2.

WORK RELATED LOST TIME ACCIDENT RATES

2.1

SUMMARY

2.1.1

Scope

This datasheet provides data on work related Lost Time Incident Rates (LTIR’s) that arise in the Exploration and Production Industry. The data are subdivided to provide guidance on typical LTIR’s that are experienced by activity, offshore, onshore, and by region. Where data are available from more than one source, multiple tables are included. Although transport and fire/explosion induced fatalities are not technically work related, they have been included for information. 2.1.2

Application

The data presented are applicable for work related accidents when undertaking QRA relating to exploration and production. Wherever possible the data selected should be those that most closely resemble the situation being modelled, rather than the more generic type of data given in the first few tables. The original data sources present the data in a variety of different ways - e.g. as LTIR’s, per 100,000 workers, per 1000 man years. These have all been adjusted to Lost Time Injury Rate per 106 exposed hours (LTIR) to facilitate comparison and use. Should it be desired to compare the FAR and the LTIR to ascertain the relative magnitude of these two indicators in a given area then the LTIR must be multiplied by 100, or the FAR divided by 100. 2.2

KEY DATA

Data Tables Table 13: Overall Lost Time Injury Rates from [1] FUNCTION Exploration Production Drilling TOTAL

1991 2.6 4.1 8.3 4.5

1992 2.0 4.2 6.2 4.2

1993 1.3 3.8 6.5 3.8

10 year AVERAGE 3.76 4.79 9.77 5.31

Note that in this table the LTIR’s for each function are calculated from the injuries and exposed hours for that function, whilst the total is all injuries and exposed hours. This explains why the total LTIR’s are not the sum of the individual function LTIR’s. Discussion The data produced by the E&P Forum [1] are probably the most comprehensive in this area as they are developed from returns by over 33 member companies world wide. It should be 13/06/2003

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noted, however, that these returns are voluntary, so that the data may not be as accurate as those presented in [2] and [3], which use statutory returns as the basis for their results. These data are generic, containing as they do offshore, onshore, Company personnel, Contractor personnel, and regional components. If a more detailed breakdown of the data is required, reference should be made to the original reports. Owing to the amount of data that would have to be manipulated, the E&P Forum reports do not sub-classify LTI’s further into accident type. Thus they should not be treated as anything other than generic figures, for indicative use when more detailed risk figures are not available from site specific studies. Table 14: Lost Time Injuries from [2] and [8] (UK) FUNCTION Production Drilling Maintenance Diving Construction(1) Deck Ops Domestic(2) Structures(3) Transport Other TOTAL FAR Notes: (1) (2) (3)

1991 38 149 111 5 98 68 57 22 6 90 644 7.57

1992 46 98 102 12 133 48 37 9 12 93 590 7.80

1993 55 72 85 21 84 39 29 11 16 52 464 5.30

AVERAGE 46.33 106.33 99.33 12.67 105.00 51.67 41.00 14.00 11.33 78.33 566.00 6.89

Includes commissioning Includes catering Includes plant and structural modifications

Discussion The validity of these values is quite high as they are developed from “voluntary” reports to the UK Health and Safety Executive. Nonetheless they should be used with care, as the average figure - included for comparative purposes - is only the mean of the values presented in the table. This is because the HSE have only been recording offshore incidents since 1991, and, prior to that, the Department of Energy only recorded serious injuries. These LTIR figures are applicable to the UK sector of the North Sea, having been collected and collated by the authorities. It would only be appropriate to use these data when considering offshore exploration and production.

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Table 15: Overall Lost Time Injury Rates from [5] (Alberta) INDUSTRY Exploration Drilling Service Rigs Other Field Services Well Operations Gas Plants TOTAL

1989 85.5 35.3 44.5 15.5

1990 89.5 28.0 37.5 19.5

1991 64.5 25.0 28.5 17.0

10 year AVERAGE 73.8 55.6 68.4 21.4

2.0 3.0 12.0

2.0 3.0 12.2

2.0 2.0 10.0

2.3 4.7 17.2

It is important to note that the definition of a lost time injury in Alberta, British Columbia and Saskatchewan is one that results in the injured being off work for 1 day or more. In most other statistics the definition of an LTI is one that entails being off work for 3 days or more. Table 16: Overall Lost Time Injury Rates from [5] (British Columbia) INDUSTRY Production Geo-seismic Drilling Service Rigs Other Services TOTAL

1989 10.5 43.5 33.5 33.5 34.5 28.0

1990 8.5 46.0 39.5 30.0 34.0 32.0

1991 8.0 45.5 25.1 7.0 20.5 21.0

5 year AVERAGE 8.3 49.9 42.9 29.3 32.1 28.3

Note that in Tables 15 and 16 the LTIR’s for each function are calculated from the injuries and exposed hours for that function, whilst the total is all injuries and exposed hours. This explains why the total LTIR’s are not the sum of the individual function LTIR’s. Discussion These data are applicable for onshore exploration and production only. It should also be remembered that the climate in the hydrocarbon producing areas of Canada can be severe, which has an adverse effect on the injury rate. These data are very accurate for the areas of Alberta and British Columbia, as they are developed from data compiled by the Worker compensation Boards in the relative provinces. The data from Alberta includes statistics from operations extracting oil from tar sands, but excludes those applicable to refineries and pipelines. The British Columbia and Saskatchewan figures apply to a similar range as appropriate. Estimating Frequencies The data presented in the tables above may be used for one of two objectives: •

To enable a Company to compare its risk figures for a specific site with typical values achieved by the Exploration and Production Industry as a whole.

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•

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Estimating the frequency of injuries resulting from work related accidents. Their use in this area should be as a first pass only, unless more detailed work is intractable. In this regard the LTIR data are slightly less varied from year to year than those for fatalities, so a greater degree of confidence may be attached to such analyses.

The frequency estimation is performed in the same way as indicated in section 1.2 above: There is a particular work activity that exposes 2 personnel to a risk of injury for 6 hours a day for 50% of the year, and has a historical LTIR of 24. The number of exposed hours

= 2 men x 6 hrs x 182 days = 2,184 hours per year.

The frequency of injury is the exposed hours multiplied by the LTIR (injuries per 106 exposed hours). Thus the frequency of injury = 2,184 x (24/106) per year = 5.24 x 10-2 per year. This is equivalent to 1 injury every 19 years. Note, however, that this is a less frequent use of these data and must be approached with a great deal of caution. This is because the LTIR cannot be used to estimate the risk of a particular injury. The outcome of a fatal accident is known - death, and risk values may be developed quite readily. With non-fatal accidents, however, there may be a multitude of consequences - for a fall these may range from a bruised arm to a broken back - which makes this analysis of less significance. The frequency of accidents may be estimated, but not their risk, unless a conditional probability can be assigned to each possible injury that may occur as a result of the accident. Comparative Statistics Comparative statistics have not been included for lost time injuries owing to their multiplicity and diversity. Analysts needing these data should approach the appropriate authorities in the areas of interest, or local accident prevention societies. Ongoing Research As with fatality statistics, the term research is not particularly appropriate. Injury statistics are collected and published on an ongoing, annual, basis by most regulatory authorities and many accident prevention societies (E.g. RoSPA in the UK). It is entirely possible, therefore, to track the performance of the industry, or a particular sector within it, to assess and analyse the trends in safety performance.

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REFERENCES 1.

Accident Data 1993, E&P Forum Report No. 6.37/212, August 1994, back to Accident Data 1985, E&P Forum Report No. 6.8/131, December 1986.

2.

Offshore Accident and Incident Statistics Report 1993, UK Health and Safety Executive Offshore Technology Report No. OTO 94/010, October 1994

3.

Development of the Oil and Gas Resources of the United Kingdom, Department of Energy, 1991, ISBN 0 11 413705 6

4.

Norwegian Petroleum Directorate, Annual Report 1993

5.

Lost Time Injuries and Illnesses, Upstream Oil and Gas Industries, Alberta 1982 1991. Alberta Occupational Health and Safety, December 1992.

6.

Casualties to Vessels and Accidents to Men, Return for 1993, Marine Accident Investigation Board.

7.

E&P Forum Member.

8.

Offshore Accident and Incident Statistics Report 1994, UK Health and Safety Executive Offshore Technology Report No. OTO 95/953, 1995

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Land Transport

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LAND TRANSPORT

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TABLE OF CONTENTS 1.

SUMMARY 1.1 Scope 1.2 Application

3 3 3

2.

WORLDWIDE STATISTICAL DATA 2.1 Road Accidents 2.2 International Comparison of Road Deaths 5

4 4

3.

UNITED KINGDOM: TRANSPORT STATISTICS 3.1 Road Transport 3.2 Risk Comparison of Transport Modes 3.3 Transport of Dangerous Substances

6 6 7 7

4.

DESERT DRIVING STATISTICS

8

5.

TRAFFIC ACCIDENTS DURING TRANSPORT OF PETROLEUM PRODUCTS

8

6.

U.S.A. DATA 6.1 Introduction 6.2 Available Data 6.2.1 Road Transport - Trucks 6.2.2 Rail Transport

9 9 9 9 10

7.

FURTHER DATA AVAILABLE

10

REFERENCES

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SUMMARY

1.1

Scope

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This data sheet provides information on land transport accident statistics for use in Quantitative Risk Assessment (QRA). The data sheet includes guidelines for the interpretation of data sources, references of which are given. Most of the data concern motor vehicles and rail transport, although some data for cyclists and pedestrians are also presented. 1.2

Application

This data sheet contains global data plus more detailed data from the USA and the United Kingdom. When using these data, it should be realised that they may not be directly applicable to the specific location under study. It is therefore strongly recommended that local data sources on accidents and transport risk from governmental or other national or regional institutions are accessed before using the data given in this sheet. Should these local data not be accessible, or their reliability/applicability be questioned, then the data in this data sheet could be used after factoring for local circumstances. The statistical information from the UK with certain assumptions can be used to derive general rules for areas elsewhere in Europe or the world: for example the influence of age and road type on accident rates. However, data which have been adjusted to allow for local circumstances should always be used with caution: the assumptions made are likely to be highly judgemental and hence may reduce the reliability of the adjusted data vis a vis reality. Each assumption shall be clearly documented so that an auditable trail is maintained.

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2.

WORLDWIDE STATISTICAL DATA

2.1

Road Accidents

Rev 0

The International Road Federation in Geneva collects world road statistics including data on road accidents from a large number of countries, [1]. The data include the annual number of accidents, annual number of injured and killed people as well as the number of injury accidents, persons injured or killed per 100 million vehicle kilometers (108 V Kms). A selection (from table VII, [1]) is given in Table 2.1 below. This table includes all those injured or killed as a result of road accidents (ie. vehicle occupants, pedestrians and other road users). It should be noted that the percentage of injury accidents in built-up areas and at night is not given below but appears in table VII, [1]. The associated traffic volume in 100 million vehicle kilometers is also given to provide an indication of the size of the sample and hence the significance (statistical reliability) of the accident rates. Table 2.1: Road Accident Fatality and Injury Rate, Selected Countries, All Vehicles, [1] Country Europe Belgium Denmark Finland 5 France 1 Germany (FRG) Great Britain Italy1 The Netherlands 2 Portugal Spain Turkey Africa Egypt Kenya Morocco 3 South Africa1 Zimbabwe 1 America Colombia Mexico USA Asia/Middle East Bahrain Hong Kong Japan 1 Kuwait Oman Yemen Oceania New Zealand

13/06/2003

Year

Traffic Volume (in108 V Kms)6 7 574.0

1991 1992 1993 1993 1991 1992 1991 1993 1993 1992 1993

383.6 8 439.0 4590.0 4618.0 4480.0 3868.2 1000.0 9 340.0 1029.0 7 308.1

1992 1990 1991 1991 1993

Injury Accident Rate (per 108 V Kms)

Injury Rate

(per 108 V Kms)

Fatality Rate

(per 108 V Kms)

101.4 23.0 14.7 29.9 69.0 55.0 44.6 172.7 69.9 189.0

143.2 27.0 18.6 41.1 90.0 76.0 62.9 48.0 233.6 104.1 336.0

3.3 1.5 1.2 2.0 1.6 1.0 1.9 1.3 7.5 4.8 21.0

4,7,9 57.0 7 52.0 nav nav 5,7 74.0

181.1 199.0 99.0 85.7 19.7

217.0 330.0 207.0 129.3 32.1

43.2 36.0 21.0 10.4 2.8

1990 1990 1992

7 509.0 554.0 36039.0

240.0 31.7 62.5

53.0 65.7 95.7

5.0 10.0 1.1

1993 1993 1993 1989 1993 1993

7 33.0 101.0 5,7 6782.0 7 148.0 5 110.0 7 103.0

50.8 157.0 106.9 137.3 24.0 83.1

79.5 209.0 129.6 20.0 53.2 76.2

1.7 4.0 1.6 2.03 4.2 13.0

1993

10 310.0

35.0

50.0

2.0

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Land Transport Notes: 1

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Rev 0

2 3 4 5 6 7 8 9 10

In accordance with the commonly agreed international definition, most countries define a fatality as being due to a road accident if death occurs within 30 days of the accident. The official road accident statistics of some countries however limit the fatalities to those occurring within shorter periods after the accident. Where different, the actual definitions are given below and should be taken into account when comparing the data in the above table: France (6 days), Italy (7 days), Spain (24 hours), South Africa (6 days), Zimbabwe (on the spot) and Japan (24 hours). Excluding casualties among cyclists. Outside cities. 1993 figure. 1992 figure. Total number of vehicle kilometers derived from table V, [1] by adding figures for each vehicle type. 2 wheeler kilometers not included (not available). 2 wheeler kilometers 1992 figure. Goods vehicle kilometers not included (not available). E&P Forum member data.

2.2

International Comparison of Road Deaths

The UK Department of Transport also provides an international comparison, namely by car user deaths (includes driver and passengers) per 100 million car kilometers, [2], table 48. The numbers will be different from those in table 1 as they exclude any pedestrians and other road users killed in the accident. A selection of this information is given in Table 2.2 below. Table 2.2: International Comparison of Road Deaths: Death Rate for Car Users by selected Countries 1992 1 [2]

Great Britain Denmark Germany Irish Republic Netherlands Finland Switzerland Australia 3 Japan 2 USA

Traffic Volume (in 108 V Kms) 4 4104 421 4618 258 950 433 473 nav nav 34844

Car User Fatality Rate (per 108 V Kms) 0.6 0.8 1.4 0.8 0.7 0.9 0.9 1.3 1.5 0.9

Notes : 1 Source: International Road Traffic and Accident Database, IRTAD, (from the Organisation for Economic Co-operation and Development, OECD). 2 Reference also note 1, table 1. To allow for the difference in definition of an accident fatality, the number of car user deaths (and therefore the car user death rate) has been adjusted according to factors used by the Economic Commission for Europe and the European Conference of Ministers of Transport, to represent standardised 30-day deaths: Japan (1 day) + 30%. 3 1991 data. 4 The total number of car kilometers was taken from table 8.4 in [3]. The car user fatality rate in column 3 is actually calculated based on total car kilometers from the International Road and Traffic Accident Database which was not available to derive car kilometers. Having the right number of car kilometers is not so relevant as it is the order of magnitude which indicates the sample size and hence the significance of the accident rates.

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3.

UNITED KINGDOM: TRANSPORT STATISTICS

3.1

Road Transport

Rev 0

The UK Department of Transport collects statistical data on transport (air, road, rail and water) and also specifically on road accidents. Only a small proportion of these are published, [3] and [1] respectively. The published information contains a great amount of detail and variety in presenting accident rates: eg. distinction is made between road types, road user types, age and sex of drivers, weather conditions etc. Table 3.1a below presents the casualty and accident rates by road type and is taken directly from [2], Table 26. The information also includes the rates at which pedestrians are either seriously injured or killed in accidents. Also available, [2], are data on the casualty rates (drivers or passengers) by age bands, road user type and severity. This information is given in Table 3.1b below. Table 3.1 a: UK Road Accident Fatality/Injury Rates: Rates by Road Class, Road User Type, Injury Severity and Pedestrian Involvement [2] Built up Roads1 Vehicle Type Pedal Cycle

Motor Cycle

Car

Bus or Coach

LGV6

HGV6

All Vehicles7

Motorways

All Roads

User3

3.3

Serious4 Inj. 87.2

Pedestr.

0.1

2.8

0.1

0.6

-

-

0.1

2.3

User

7.6

177.8

15.2

136.6

2.8

35.7

10.2

153.9

Pedestr.

1.9

17.7

0.6

1.1

-

-

1.3

10.4

User

0.3

5.8

0.9

8.3

0.2

2.0

0.5

6.3

Pedestr.

0.4

5.8

0.1

0.4

0.0

0.0

0.3

2.8

User

0.6

20.4

0.5

6.1

2.3

5.3

0.8

15.1

Pedestr.

2.0

11.7

0.2

0.9

0.0

0.2

1.3

7.6

User

0.1

2.3

0.4

3.6

0.2

1.6

0.3

2.7

Pedestr.

0.5

3.5

0.1

0.2

0.0

0.0

0.2

1.6

User

0.1

1.8

0.2

2.5

0.2

1.5

0.2

2.0

Pedestr.

1.3

2.9

0.3

0.2

0.1

0.1

0.5

0.9

User

0.4

9.5

1.0

9.1

0.3

0.2

0.6

8.2

Pedestr.

0.5

5.8

0.1

0.4

0.1

0.1

0.3

2.8

Person

Death5

Non Built up Roads1 Death Serious Inj. 6.7 57.0

Death

Death

-

Serious Inj. -

4.1

Serious Inj. 79.9

All Rates in deaths or injuries per 100 million vehicle kilometers 2.

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Notes to table 3.1a: 1 Built up roads are roads with speed limits (ignoring temporary limits) of 40 mph or less, non-built up roads with speed limit of over 40 mph, but excluding motorways. Numbers include road class not reported. 2 Total amount of kilometers for the particular vehicle type on all road types, table 1 (b) in [2]. Numbers are included in the table to provide an indication of the sample size, hence significance (reliability) of the derived casualty rates. 3 User of a vehicle covers all occupants, i.e. driver (or rider) and passengers. 4 Serious injury is an injury for which a person is detained in hospital as an 'in-patient', or fractures, concussion, internal injuries, crushings, severe cuts and lacerations, severe general shock or injuries causing death 30 or more days after the accident. 5 Within 30 days after the accident. 6 Heavy Goods Vehicles (HGV) are those over 1.524 tonnes unloaded weight. Light Good Vehicles (LGV) are those under 1.524 tonnes unloaded weight. From 1 January onwards the border line will be 3.5 tonnes. 7 All motor and non-motor vehicles (include those mentioned in Table 3.1a). Examples of other such motor vehicles are ambulances, fire engines, pedestrian controlled vehicles with a motor, railway trains or engines, refuse vehicles, road rollers, tractores, excavators, mobile cranes, tower wagons, army tanks etc. The rate of occurrence of injury accidents for “all Vehicules” is derived using a higher total vehicular mileage, that being the mileage for all vehicles.

Table 3.1 b: UK Road Transport Accident Rates 1993 Casualty Rates (per 108 V Kms) Male Age 17-20 21-24 25-28 29-33 34-38 39-43 44-48 49-53 54-58 59-63 64-68 69-73 74+ All

3.2

Fatal 1.8 0.6 0.4 0.3 0.2 0.2 0.2 0.2 0.3 0.2 0.3 0.5 2.0 0.4

Fat.al/Serious Injuries 20 7 5 4 2 2 2 2 3 3 3 5 12 4

Female All Severities 134 53 33 28 20 17 14 15 16 17 18 25 54 27

Fatal 0.8 0.2 0.2 0.2 0.2 0.1 0.2 0.1 0.2 0.3 0.9 1.2 2.8 0.3

Fatal/Serious Injuries 15 7 5 5 4 3 3 4 4 4 7 11 20 5

All Severities 155 80 61 55 43 36 35 36 37 35 44 55 92 53

Risk Comparison of Transport Modes

Howard Collins, Statistics Directorate, UK Department of Transport, gives useful guidelines in an article in [3] for comparing various modes of passenger transport and concludes that the type of casualty rate used will influence the results of the comparison. On the basis of casualty rate per passenger kilometer driving in a car appears to be much more dangerous than travelling by air. However, on the basis of casualty rate per passenger hours the risk is the same and calculated in passenger journeys the travelling by air is more dangerous. It is hence important when choosing the type of casualty rate for a comparative study, to establish which type best describes the risk perceived relevant for the study. 3.3

Transport of Dangerous Substances

[20] Provides a comprehensive overview and risk assessment of major hazard aspects of transport of dangerous substances in the UK. The scope covered not only the consideration of major hazard aspects of the transport of dangerous substances, but also the identification of 13/06/2003

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appropriate control measures and advice on any additional action that might be necessary. It does not include radioactive substances, transport by air or by pipelines or risks to the environment. 4.

DESERT DRIVING STATISTICS

One of the E&P Forum member companies collects statistical data on accidents from which accident rates for desert driving conditions can be calculated. This data covers a period between 1992 and 1994. The derived desert driving accident and fatality rates are shown in Table 4 below and relate to company and contractor work related accidents. Table 4: Desert Driving Accident and Fatality Rates (Graded Road and Off Road) Year

Road Traffic Accidents 137

Injuries

Fatalities

1992

Road Traffic (108 V Km) 1 0.79

56

4

Fatality Rate (per 108 V Kms) 5.1

1993

0.89

135

42

2

2.3

1994

0.86

111

26

0

0.0

Note: 1 As the number of kilometers driven on graded roads & off road is not reported separately, this number is derived from the total number of kilometers by assuming that 75% of the driving takes place on graded roads or off road.

The downward trend in the Fatality Rate is considered to be the result of improved induction training, the fitting of roll-over bars and speed governors to all LGV's and the near 100% usage of seat-belts. This needs to be taken into account when applying the rates for desert driving at other locations. 5.

TRAFFIC ACCIDENTS DURING PETROLEUM PRODUCTS TRANSPORT

One E&P Forum member collected data on accidents involving Heavy Goods Vehicles carrying petroleum products including fatal accident rates, for various areas in the world. This is presented in Table 5 below. Table 5: 1993 Fatal Accident Rates for Heavy Goods Vehicles carrying Petroleum Products Area

Number of Vehicles

Vehicle Traffic (in 108 V Kms)

Number of Accidents

Number of Fatal Accidents

Western Hemisphere and Africa Europe

5917

3.3

710

44

Fatality Rate (in 108 V Kms) 13.5

5255

3.1

529

7

2.3

Far East and Australia Middle East, Francophone Africa and South Asia CIS, Central and East Europe All Areas

5026

3.2

248

32

10.1

818

4.0

56

3

7.5

119

0.4

49

0

0

17135

10.0

1592

86

8.7

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6.

U.S.A. DATA

6.1

Introduction

Rev 0

This section provides gives information about land transport risks in the USA, as informed by an E&P Forum member. The information presented in this section has been extracted from a report compilation, [4]. Reference [4] provides information for explosive, flammable and otherwise dangerous chemicals. The handbook provides methodologies for assessing the potential impacts of hazardous material releases and addresses hazard analysis (hazard identification, vulnerability analysis and risk analysis). This section presents failure rates which originate from several sources. The age of the background data and the individual sources may no longer reflect the reliability of transport vehicles on the roads and railways today because of stricter safety regulations for both vehicles and materials transportation. 6.2

Available Data

6.2.1

Road Transport - Trucks

Table 6.2.1:

Frequently Cited Average Accident Rates from various Literature Sources, compiled by FEMA [4] Vehicle

Accident Rate (per mile) 5.0 x 10-6

Trucks in the petroleum industry.

Reference API, 1983 [5]

Trucks.

2.5 x 10-6

All trucks.

1.2 x 10-5

Dennis at al 1978 [6] Rhoads et at 1978 [7] National Safety Council, 1988 [9]

Bulk hazardous materials trucks.

1.5 x 10-6

Ichniowski, 1984 [10]

The rate of accidents can be a function of road type (urban, rural, etc), number of lanes, traffic density, average speeds, type of vehicle, number of intersections, road conditions, weather conditions, geometry of the road, grade, etc. However, differences attributed to these various causes tend to give results that are within roughly one order of magnitude, with the range usually being 1 to 10 x 10-6/mile or between one and ten accidents per million miles driven, [11], [5], [8] and [9]. Rates have been reported for specific locations or road types. Much of the variation in these average rates can be explained by level or compliance with reporting requirements and different reporting thresholds in terms of damages sustained for the various data bases, as well as the road and weather conditions in the subject area. Table 6.2.2: Reference

Fraction of all reported accidents resulting in a spill or discharge Source

Fraction Resulting in a Spill or Discharge

[12]

US Environment Protection Agency

0.2

[13]

OTA, Office of Technology Assessment

0.115

[14]

U.S. Department of Energy

0.3

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Land Transport [15]

E&P Forum QRA Datasheet Directory U.S. Department of Transportation

Rev 0 0.46

Others

10 kg/sec 70 mm

Valves < 2" > 2"

6.13 x 10-4 6.13 x 10-4

2.62 x 10-4 1.51 x 10-4

0 1.11 x 10-4

Flanges < 2" > 2"

3.96 x 10-4 3.96 x 10-4

1.31 x 10-4 9.79 x 10-5

0 3.26 x 10-5

Process piping > 2"

1.14 x 10-5

2.82 x 10-6

1.31 x 10-6

Instrument connections/small bore fittings < 3/4" > 3/4"

1.64 x 10-5 1.35 x 10-4

4.08 x 10-4 1.87 x 10-4

0 0

Pressure vessels

0.89 x 10-4

1.3 x 10-4

1.5 x 10-4

Excluding all valves, piping, fittings beyond the first flange and the flange itself

Centrifugal pumps

2.49 x 10-2

1.27 x 10-3

1.11 x 10-4

Excluding all valves, piping, fittings beyond the first flange and the flange itself

Heat exchangers

5.8 x 10-3

6.8 x 10-3

6.81 x 10-3

Excluding all valves, piping, fittings beyond the first flange and the flange itself

Centrifugal compressors

1.65 x 10-2

8.42 x 10-4

1.03 x 10-4

Excluding all valves, piping, fittings beyond the first flange and the flange itself

Leak category Leak rate Typical hole size Equipment

Including flange joints

Excluding any flanges and valves

A pipe section is defined as a length of pipe with two welds and three flanges. The application of this to estimating release frequencies requires judgement. If the data areavailable, an approach by counting flanges is more transparent, but also rather time consuming. Given potential variations resulting from different fabrication, installation and maintenance, it may be questioned whether additional effort will be reflected in the accuracy of the final results. 13/06/2003

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The leak sizes described as medium and large are given typical sizes of 860 mm2 (33 mm dia) and 4300 mm2 (74 mm dia) respectively.

2.2

Models for Prediction of Release and Dispersion

2.2.1

Models for Release Frequencies

The release frequencies given in table 2.5 and other sources are normally based on historical failure data for a given population combined with use of expert judgement. The release frequencies from any particular type of mechanical equipment are normally regarded as constant for the time period covered by a risk analysis.

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3.

IGNITION

3.1

Fire/Explosion: Historical Data

Rev 0

Historical data for ignitions (fire and explosion) on offshore production and processing installations are shown in Table 2.1. Table 3.1

Typical frequency of process release and ignition for offshore production and processing

Type of Event

Facility Type

Area

Ref.

Rate (x10-3 unit yr)

All fires/explosions

fixed floating

Worldwide Worldwide

A A

Significant release Ignited release

fixed fixed

UK North Sea UK North Sea

B B

2 600 250

Fires Explosions

fixed fixed

UK North Sea UK North Sea

C C

280 50

All fires/explosions Severe fires/explosions

fixed fixed

Norw.+UK North Sea Norw.+UK North Sea

D D

180 6.5

All fire/explosion

fixed

Gulf of Mexico

E

20

Fires/explosions (severe local damage)

fixed

Gulf of Mexico

E

1.2

Fires/explosions (severe platform damage)

fixed

Gulf of Mexico

E

0.4

Fires/explosions (platform lost)

fixed

Gulf of Mexico

E

0.1

3.7 13

References: A - [2]- WOAD (1990); B - [4]-E&P Forum member; C - [6]- Ashmore; D - [8]- Veritec; E - [5]- DNV Gulf of Mexico Because WOAD collects data from public domain reports it is judged that it will be biased towards major accidents (i.e. minor accidents will not feature in newspapers or radio/TV reports). The values in Table 3.1 should therefore be used as global values, applicable to large integrated platforms. Another source of global data is shown in Table 3.2 ([1]- E&P Forum member), which shows the difference between old and modern installations, as well as various platform sizes.

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Table 3.2

E&P Forum QRA Datasheet Directory

Rev 0

Fire/explosion frequency by installation type No of fires/ explosions

Platform years

Fire/explosion per platform-year

Large, oil, pre 1980 Large, oil, 1980-90 Gas complex Small integrated Unmanned

13 1 1 1 0

264 81 300 170 245

0.049 0.012 0.003 0.006 20 kg/sec)

Major gas release (2-20 kg/sec)

Minor gas release (< 2 kg/sec)

0.439 0.364 0.256 0.168 0.443

0.114 0.105 0.043 0.026 0.130

0.012 0.030 0.005 0.043

Typical probability of ignition of gas releases (bridge linked platform) Location of release Lower deck (Riser above sea Subsea

Massive gas release (> 20 kg/sec)

Major gas release (2-20 kg/sec)

Minor gas release (< 2 kg/sec)

0.046 0.078 0.140

0.006 0.013 0.051

0.001 0.002 0.002)

Typical probability of ignition of oil releases (calculate gas flash and treat as gas release) Location of release Module Riser above sea Subsea

Massive oil release (> 20 kg/sec)

Major oil release (2-20 kg/sec)

Minor oil release (< 2 kg/sec)

0.121 0.051 0.005

0.091 0.009 0.001

0.003 0.003 -

Probabilities of ignited gas releases associated with releases from risers, subsea installation and pipelines are also given in the data sheet on Risers and pipelines. It follows that statistics associated with risers etc. should be verified with both Table 3.8 and that Datasheet.

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3.3

Models for Prediction of Fire and Explosion Consequences

3.3.1

Models for Ignition

Rev 0

The minimum ignition energy for different flammable gases differs significantly, but for Methane, Ethane, Propane and other relevant natural gases these energies are generally low. Sparks generated from static electricity may therefore easily ignite a flammable gas cloud. Hot surfaces and open flames are other potential ignition sources. Ignition models include these and other sources and they are based on experimental data combined with expert judgement. Several computer programmes include models for ignition of flammable gases and liquids. The models are based on theoretical assessments and, only to a minor extent, empirical data. The prediction of ignition probabilities as a function of gas dispersion, reflecting the equipment and activities in the areas, is uncertain and in considerable need of more refined modelling. A Joint Industry Project carried out by DNV Technica (N), Scandpower (N), AEA Technology (UK) and COWIconsult (DK) is directed at improvement of the modelling in this field. The project is scheduled to be complete at the end of 1996. It is expected that the historical data for ignitions will improve when the E&P Forum project on HC leak and ignition data collection is further progressed. [10] [11] [12].

3.3.2

Models for Fire and Explosions

As for dispersion, there are several models for fire and explosion calculations. For fire calculations the models cover jet fires, fireballs (BLEVEs), pool fires, flash fires etc. For explosion calculations, there are also several models depending on physical or chemical energy sources, and for gas explosions (deflagration, detonation). There are several computer programmes that can calculate fire and explosion phenomena based on the above mentioned types. The models used by the programmes include simple models of the release phenomena, to detailed state of the art Computational Fluid Dynamics (CFD) calculations.

3.3.3

Models for Release Consequence Analysis

When modelling accidental releases the most critical step is to estimate the amount released per second and the dependence of the release rate with time. The nature of the release will depend on the state of the material within the containment; gaseous, 2-phase, liquid, a boiling liquid or sub-cooled liquid. The dispersion of jet releases, plume releases, area sources and instantaneous releases are calculated using models specific to the mode of release and the density of the gas. Models of evaporation from a pool on the ground or spill on water are also available. The released substance can either be flammable or toxic or both. Reference [13], (pages 431-439) gives further explanation of parameters which affect dispersion. There are several computer codes that can calculate dispersion based on the above mentioned release types. The models used by the computer codes include simple to detailed models of the release phenomena, and state of the art CFD calculation.

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4.

MISCELLANEOUS

4.1

Vapour Cloud Explosions

Rev 0

Table 4.1 Vapour cloud explosions 1920-1985 (onshore) [13] Material involved Methane LPG Petroleum Spirit Propane Butane Others Circumstances Incidental release Operational release Ignition source Permanently present Incidentally present

Number of cases 167 46 39 35 30 93

Percentage 41 11 10 9 7 22

Causes Leakage Careless handling Bursting/rupture Continuous Instantaneous

Percentage 27 22 44 1 6

Normally expected Not expected Normally expected Not expected

49 3 44 4

Delay before ignition Delay time (min) 30 Unknown

Percentage 19 40 12 5 6 18

Drift distance (m) 1000

58 38 4

The table is based on a total of 410 vapour clouds explosions forming a database covering onshore incidents in the period 1920-1985. The incidents were selected on the basis of causing serious material damage due to explosion (not just flash fire). The data indicates that most explosions ignite early and that delayed ignition reduces the likelihood of an explosion. However, delay does not by itself eliminate the chance of a vapour cloud explosion, as some explosions have been ignited over 1 kilometre from the vapour source.

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Table 4.2

Release and dispersion Outflow calculations, typical for organic liquids and for vapour methane and propane

Reference

FRED 2.2 software package (Liquid/Vapour outflow from a hole)

The calculations include several assumptions and parameters: CH4: Cp/Cv = 1.31 C3H8:

Cp/Cv

= 1.13

m

= 16 kg/kmol

m

= 44 kg/kmol

CD

= 0.8

CD

= 0.8

t

= 25 °C

t

= 25 °C

CD

= 1000 kg/m3 = 0.61

CD

= 700 kg/m3 = 0.61

Head

=5m

Head

=5m

Liquid 1:

Liquid 2:

Caution: pressure in bara Do not use the values given in this table for design! Source Pressure [bara]

Release rate [kg/s], steady state for release hole sizes in [inches] Liquid 1 Liquid 2 Vapour CH4 =1000 =700 1"

2"

1"

2"

1"

Vapour C3H8 2"

1"

2"

2

5.3

21.

4.4

18.

0.14

0.55

0.22

0.87

5

9.2

37.

7.7

31.

0.34

1.4

0.54

2.2 4.3

10

13.

54.

11.

45.

0.69

2.8

1.1

25

22.

86.

18.

72.

1.7

6.9

2.7

11.

50

31.

123.

26.

103.

3.4

5.4

22.

14.

75

38.

151.

32.

126.

5.2

21.

100

44.

174.

36.

146.

6.9

28.

11.

8.1

43.

32.

125

49.

195.

41.

163.

8.6

34.

14.

54.

150

53.

214.

45.

179.

10.

41.

16.

65.

175

58.

231.

48.

193.

12.

48.

19.

76.

200

62.

247.

52.

207.

14.

55.

22.

87.

Notes 1

The calculations shown in Table 4.2 are from the FRED package, release 2.2 , a non commercial PC based package. FRED stands for 'Fire, Release, Explosion, Dispersion' and is a suit of validated PC based physical effects models.

2

The calculations indicate the scale of release for a given hole size (Table 4.2) and the potential size of the resulting flammable zones (Table 4.3). They should not be used as a basis for engineering; the specific calculations appropriate to a given engineering situation should be calculated on a case specific basis.

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Table 4.3

Release and dispersion Distance to LFL in open air plume

Reference

FRED 2.2 software package (AEROPLUME: Jet dispersion model from Shell HGSYSTEM)

The calculations include several assumptions and parameters: CH4: LFL = 53,000 ppm C3H8: m

= 16 kg/kmol

LFL

= 22,000 ppm

m

= 44 kg/kmol

Ambient Temperature Humidity

20 °C 70 %

Reference Height Sample Time

10 m 18.75 seconds

Surface Roughness

0.3 m

Reservoir Pressure

1.2 bara

Release Height

10 m

Reservoir Temperature

20 °C

Note: Release is oriented downwind for worse case Hole size is minimum for required mass flow rate Do not use the values given in this table for design! Mass Flow

Hole Size

Rate

[mm]

Distance to LFL [m] Methane 2D

5D

Hole Size 2F

1 1.5

90.7 111

9 11

9 11

10 12

2

128

13

12

14

3

157

15

15

4

181

17

5

203

6 7

[mm] 73.1 89.5

Distance to LFL [m] Propane 2D

5D

2F

10 12

10 12

12 14

103

14

14

16

17

127

17

16

20

17

19

146

19

18

22

19

18

21

163

22

20

25

222

21

20

23

179

23

22

27

240

23

21

25

193

25

23

29

8

256

24

22

26

207

27

24

31

9

272

25

23

28

219

28

26

33

10

287

27

25

29

231

30

27

34

12.5

321

30

27

33

258

33

29

38

15

351

32

29

36

283

36

32

41

17.5

379

35

31

38

306

39

34

44

20

405

37

33

41

327

41

36

47

30

497

44

39

49

400

50

42

57

40

573

51

45

56

462

57

48

64

50

641

56

49

62

517

63

52

71

75

785

68

58

75

633

92

62

102

100

907

78

66

86

731

115

78

125

Notes 1

In the calculations in Table 4.2, the reference height was 10m for the source, and the distances given are centre-line distances.

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Table 4.3

Release and dispersion Cloud dimensions of a dense propane vapour cloud

Reference

FRED 2.2 software package (HEGADAS: dense gas model from Shell HGSYSTEM, steady state)

The calculations include several assumptions and parameters: Air Temperature Gas Temperature 20 °C

-42 °C

Surface Temperature

20 °C

Specific Heat

106 J/mol K

Humidity

70 %

Molecular Weight

44 kg/kmol

Surface Code

3 (land with heat exch.)

Reference Height

10 m

Surface Roughness

0.3 m

Sample Time

Instantaneous

LFL conc.

22,000 ppm

Heat Group for nat conv

29.00

Do not use the values given in this table for design! Source Dimension Rate

Cloud dimension, for LFL contour [m] 5D Length

2F

[m]

[kg/s]

Half width

Length

Half width

2.2 5

1 5

13 31

5 12

21 54

36 85

7.1

10

45

17

80

120

11.2

25

76

27

137

200

15.8

50

112

39

204

290

Notes 1

In the presented calculations of heavy gas dispersion the basis is a pool of propane at atmospheric boiling point evaporating from a free pool. This is a very conservative estimate of the evaporation rate. For a more accurate evaporation rate calculation other models are available.

2

Dispersion and mixing in confined spaces with equipment, such as an offshore module, will follow more complex mechanisms. In general turbulence round equipment would accelerate mixing. However, pockets of air may also be formed where air movement is limited and mixing will be slow. These effects can be studied in a wind tunnel or using computer models.

3

In the table, 5D and 2F refer to the windspeed (metres per second) and Pasquill stability class (A through F)

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Table 4.4

Release and dispersion Effect of stability on dispersion/dilution of methane Distance to LFL with different stabilities.

Reference

FRED 2.2 software package (AEROPLUME: Jet dispersion model from Shell HGSYSTEM)

The calculations include several assumptions and parameters: Ambient Temperature Gas Temperature 20 °C

-42 °C

Humidity

70 %

Reservoir Pressure

1.2 bar

Wind Speed

2 m/s

Reservoir Temperature

20 °C

Surface Roughness

0.3 m

Reference Height

10 m

LFL conc.

53,000 ppm

Sample Time

18.75 seconds

Release Height

10 m

Note: Release is oriented downwind for worse case Hole size is minimum for required mass flow rate Do not use the values given in this table for design! Pasquill stability

[kg/s] 1

5

class

10

50

Distance to LFL [m]]

A B

8 9

17 18

23 25

45 50

C

9

20

27

56

D

9

21

28

57

E

10

21

28

57

F

10

21

30

62

Notes 1

Table 4.4 shows the magnitude of stability effects on dispersion distance for methane. Class D is by far the most common condition outdoors in the UK. Other conditions can always occur but they generally (but not in all cases) have only a slight effect on predicted dispersion distances.

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Table 4.5 Reference

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Typical flame sizes for ignited releases of process hydrocarbon FRED 2.2 software package (Shell Research model for gas flare radiation)

The calculations include several assumptions and parameters: Gas Composition 80% Methane

10% Ethane

6% Propane

4% Nitrogen

Ambient Temperature

20 °C

Humidity

70%

Fuel Temperature

20 °C

Release Height

10 m

Note: Release is oriented downwind for worse case Do not use the values given in this table for design! 2 inch diameter hole Mass Flow Rate No Wind [kg/s] Length 1 15.1 5 28.0 10 37.4 20 50.2 100 100.2

Vertical Wind=5m/s Length Width 8.4 2.6 15.7 4.7 20.9 6.2 28.0 8.2 56.0 16.6

No Wind Length 11.9 22.3 29.6 39.5 77.8

Horizontal Wind=5m/s Length Width 12.9 1.6 23.3 3.0 31.0 4.1 41.5 5.9 82.2 13.5

6 inch diameter hole Mass Flow Rate No Wind [kg/s] Length 1 20.7 5 33.2 10 41.2 20 53.4 100 103.1

Vertical Wind=5m/s Length Width 11.1 5.1 18.4 6.2 22.9 7.1 29.8 9.0 57.7 16.9

No Wind Length 14.8 24.0 31.6 41.2 79.3

Horizontal Wind=5m/s Length Width 20.7 2.1 28.3 4.7 35.2 5.7 44.9 7.3 85.0 14.9

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Figure 4.1 Thermal radiation from an ignited 2 inch release

2 inch diameter hole 200 180

Dist to 1.5kW/m2

160 140 Vertical/No Wind

120

Vertical/5m/s Wind

100

Horizontal/No Wind

80

Horizontal/5m/s Wind

60 40 20 0 0

20

40

60

80

100

Mass Flow Rate

Figure 4.2 Thermal radiation from an ignited 6 inch release

6 inch diameter hole 200 180

Dist to 1.5kW/m2

160 140 Vertical/No Wind

120

Vertical/5m/s Wind

100

Horizontal/No Wind

80

Horizontal/5m/s Wind

60 40 20 0 0

20

40

60

80

100

Mass Flow Rate

Notes 1

Distances to 1.5kW/m2 are downwind distances (where applicable) and are at release height (10m)

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Table 4.6

Pool Fire and BLEVE Typical sizes and effects of ignited releases of process hydrocarbon

Reference

FRED 2.2 software package (Shell Research model pool fire radiation model and Shell Research BLEVE model)

The calculations include several assumptions and parameters: Pool fire Fuel

Kerosine

Ambient Temperature

20 °C

Humidity

70%

Windspeed

2 m/s

Radiometers are at ground level, oriented to maximum and downwind BLEVE Fuel

40% Propane, 60% Butane

Fill ratio

80%

Humidity

70%

Instruments are at ground level

Fuel Temperature

20 °C

Ambient Temperature

20 °C

Bold for interpolated results

Do not use the values given in this table for design! Table A

Pool fire typical dimensions and effects Pool Distance [m] from pool to given radiation level [kW/m2]

Diameter

Area

1.5

5

12.5

25 7.4 9.2

5 10

20 80

31 46

19 27

12 16

25

500

66

36

19

11

50

2000

98

51

21

12

Table B

BLEVE Fireball: typical dimension, duration and effects

Mass

Diameter

Duration

Distance [m] to given % fatality (Lees)

[tonnes]

[m]

[s]

50

10

1

1 5

43.8 74.9

11.1 15.0

20 36

20 37

20 40

10

94.4

16.4

47

47

52

25

128.8

19.2

69

70

78

50

161.4

21.1

89

91

100

100

203.3

24.8

117

121

139

250

275.9

30.0

166

178

206

500

347.7

35.2

218

243

280

Notes 1 The tabulation of typical fire sizes and effects is given for those who are not familiar with the scale and severity of such events. The data in the Tables are for guidance only. Calculations should be made appropriate to a given engineering situation.

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Research

There are several ongoing research and development projects within the area of release, dispersion, ignition and fires/explosions. It is expected that these projects will influence the models used, and substitute for lack of historical or relevant data; focus the attention of the industry on the need for quality historical data. Release frequencies: • E&P forum leak and ignition database • UK HSE release data for UK sector Ignition models: • Joint Industry Project: Ignition Modelling (1995-96) with DNV Industry, Scandpower, AEA Technology and COWIconsult. Fire and Explosion modelling • Joint industry project on Blast and Fire engineering with The Steel Construction Institute. • Gas safety Programme 1993-96. CMR, Bergen. • Fire on Sea (1993-96), SINTEF/NBL. It is expected that the historical data for release frequencies will improve when the E&P Forum project on HC (hydrocarbon) leak and ignition data collection has been established. The work was started in 1990-92 as a feasibility study whereby a database was established, and the structure and procedures for a more comprehensive database were decided as a follow-up. Ref. [10] [11] [12]. A similar database to the one being developed by E&P Forum is established by UK HSE (Health and Safety Executive). The data input are provided by all UK operators, however, HSE will only make summary reports available for the public and potential users. No intention or possibilities are at present made to integrate the HSE database with similar data from other regions/areas. A major problem with historical data on releases is associated with the leak rate and leak volume. It is acknowledged (ref. [11]) that hole sizes are one of the most difficult parameters to collect, and various methods are offered.

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5.

REFERENCES

5.1

E&P Forum member

5.2

DNV, 1990: Worldwide Offshore Accident Data, Statistical Report 1990, Det Norske Veritas

5.3

DNV, 1994: Worldwide Offshore Accident Data, (WOAD) Det Norske Veritas, 1994

5.4

E&P Forum member

5.5

Sofyanos, T., 1981: Causes and Consequences of Fires and Explosions on Offshore Platforms: Statistical Survey of Gulf of Mexico Data, DNV Rep 81-0057

5.6

Ashmore, F.S., 1989: The Design and Integrity of Deluge Systems, Proceeding of conference on Contingency Planning for the Offshore Industry, Aberdeen, January 1989

5.7

Technica (UK), 1990: Riser Safety Evaluation Routine, Report issued by an E&P Forum member, 90-1045, April, 1990

5.8

Veritec, 1988; Reassessment of Fatal Accident Frequency Rates for Troll Gas only Topsides, Report 88-3101

5.9

DNV Technica; ARF Technical Note T5, 1996.

5.10

Hydrocarbon Leak and Ignition Data Base Prepared for E&P Forum by DNV Technica Project No. N658, 20. February 1992 Issued as EP report EP 92-0503.

5.11

Guidelines for HC Leak and Ignition Data Collection Prepared for E&P Forum by DNV Technica Project No. N658, 20. February 1992 Issued as EP report EP 92-0577.

5.12

Calibration of HC Leak Frequency and Ignition Probability Data Prepared for E&P Forum by DNV Technica Project No. N658, 20. February 1992 Issued as EP report EP 92-0504.

5.13 Loss Prevention in the Process Industies F. P. Lees Butterworth, 1980, ISBN 0-408-10604-2. 5.14 The Offshore Hydrocarbon Release (HCR) Database R. A. P. Bruce (HSE Offshore Safety Division) ICHEME Symposium Series No. 139.

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RISER AND PIPELINES LEAKS

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TABLE OF CONTENTS

1. 1.1 1.2

SUMMARY ..............................................................................................................3 Scope ........................................................................................................................3 Application ...............................................................................................................3

2. 2.1

2.2 2.3 2.4

KEY DATA .............................................................................................................. 3 Offshore Pipelines ................................................................................................... 3 2.1.1 Population Data ..............................................................................................3 2.1.2 Incident Data ..................................................................................................4 2.1.3 Frequency Estimates ......................................................................................5 2.1.4 Discussion ......................................................................................................8 Onshore Pipelines .................................................................................................. 10 Ignition Probability ............................................................................................... 11 Umbilicals .............................................................................................................. 12

3.

ONGOING RESEARCH ...................................................................................... 13

4.

REFERENCES ...................................................................................................... 14

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SUMMARY

1.1

Scope

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This data sheet covers loss of containment from pipelines and risers. Data are presented for both steel pipes and flexibles, and detailed for a number of factors influencing the frequency of loss of containment. Only incidents involving loss of containment are included in this data sheet. However, Ref. [1] also contains data on riser and pipeline incidents which did not result in leaks, but possibly caused repair activities and production down time. Hence, assessment of risk to personnel and to the environment is prioritised, while risk of loss of production is not. Estimates of ignition probabilities of a release from pipelines and risers are also given. A section on reliability data of umbilicals is also included. This comprises umbilicals used for production and injection well control as well as pipeline safety valve control. 1.2

Application

Emphasis is put on offshore installations in the North Sea. However, data from the Gulf of Mexico and from onshore pipelines are presented for reference. The data sheet gives details on a number of factors that can influence the failure rate for pipelines and risers. However, it should be noted that individual pipelines may have very different properties, characteristics and functions, many of which may not have been considered to the required detail here. Therefore, it is recommended that in hazard and risk analysis each pipeline should be assessed on its own merits. 2.

KEY DATA

2.1

Offshore Pipelines

The data presented in this data sheet is taken from the PARLOC 92 report by AME [1], if not otherwise stated. Reference [1] describes a comprehensive database analysis performed on behalf of the Health and Safety Executive (HSE). The study covers the various sectors of the North Sea. Incidents included are sourced from information held by Regulatory Authorities and Pipeline Operators. Each incident has been subject to thorough investigation. A correlation of the data also included follow-up clarification of incident details. The HSE report is generally recognised as the best source of North Sea data, and supersedes previous work by consultants and companies for this area. The number of incidents in [1] is 295 with 201 involving operating pipelines and risers (incl. fittings), the remainder occurring during construction, hydrotest etc. Of the 201 incidents, 94 caused loss of containment. At the date of the report (by end of 1991) there were 794 pipelines in the North Sea with a total length of about 15770 km, representing almost 130000 km-years of operation. In addition, data on 902 risers with a total of approx. 7700 years of operational experience is included.

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2.1.1 Population Data Population data for the North Sea is given in Table 1. Tables 2 and 3 present the corresponding operating experience that is used as a basis for the frequency estimates. Table 1: Number of North Sea Pipelines in the AME Database Line Type Contents of Pipeline Diameter (in) Oil Gas Other Flexible lines 77 25 27 Steel lines 227 300 138 2" to 8" 115 80 121 10" to 16" 54 101 16 18" to 24" 33 72 1 26" to 36" 25 47 0 Total 304 325 165 Note 1.1: Flexible lines are mainly in the range of 2"-8" diameter.

Total 129 665 316 171 106 72 794

Table 2: North Sea Pipeline operating experience in km-years to end of 1991 Line Type Diameter (in) Flexible lines Steel lines 2" to 8" 10" to 16" 18" to 24" 26" to 36"

Oil 862.4 36,961.9 3,239 6,146.6 7,743.3 19,833

Contents of Pipeline Gas Other 129.9 255.9 80,287.4 10,600 1,731.9 10,184.2 9,902.8 400.1 14,536.1 15.7 54,116.6 0

Total 1,248.2 127,849.3 15,155.1 16,449.5 22,295.1 73,949.6

Table 3: North Sea riser operating experience in riser-years to end of 1991 Line Type Diameter (in) Diameter (in) Flexible lines Steel lines 2" to 8" 10" to 16" 18" to 24" 26" to 36"

Oil 2,095.8 446.5 622.1 721.2 306

Contents of Pipeline Gas Other 3,798.1 310.9 1,270.7 1,316.3 900.2

1,411 1,318.5 83 9.5 0

Total 404.1 7,304.9 2,075.9 1,975.8 2,047 1,206.2

2.1.2 Incident data The database contains incident data as given in table 4 and 5 below. Only data related to loss of containment from operating pipelines and risers (48 incidents) is analysed in the following chapters.

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Table 4: Incidents involving pipelines and risers Consequence of incident Status of pipeline at No of incid. No hole Hole in 0-20mm 20-80mm > 80mm incident pipeline hole hole hole Operating 138 90 48 27 7 13 Shut down 9 8 1 1 Under construction 55 39 15 2 13 Before 11 10 1 1 commissioning Hydrotest 12 4 8 2 1 5 Commissioning 2 1 1 1 Total 227 152 74 32 9 32 Note 4.1:"Shut down" denotes pipelines no longer in operation at the time of the incident. Table 5: Incidents involving fittings

Status of pipeline at incident Operating Shut down Under construction Before commissioning Hydrotest Commissioning Total

Number of incidents 63 0 0 1 3 1 68

Consequence of incident No leak Leak 0-20 mm 20-80 hole mm hole 17 46 37 8

> 80 mm hole 1

1 1 19

2 1 49

2 39

8

1 2

2.1.3 Frequency estimates The following tables give frequency estimates for loss of containment from risers and pipelines. The estimates are sorted, based on the governing factors affecting the frequency, as analysed in [1]. These are: • • • • •

Location of the leak (riser, platform safety zone, subsea well safety zone or mid-line) Incident cause Diameter of pipeline Length of pipeline Contents of pipeline

In addition, the possible effect of a number of other factors are discussed in relation to the frequency estimates (see notes). It must be noted, however, that the assessment of the effect of the factors are based on a very small number of incidents, and should consequently be interpreted with care. In the calculation of frequencies in Tables 6-8, it is assumed that the number of incidents follows a Poisson distribution. Based on this assumption, the upper 95% and lower 5% confidence limits for each estimate have been calculated. For all categories where no incidents are recorded, a best estimate of 0.7 incidents and an upper bound of 3 incidents are assumed. 13/06/2003

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Table 6: Frequency (per 104 years) of loss of containment for risers [1] 5.4 Diameter Experience Number of Lower Best (riser-years) incidents bound estimate Steel lines 2" to 8" 2083 1 0.24 4.8 > 10" 5249.2 5 3.75 9.53 10" to 16" 1995.9 4 6.86 20 6 .2 ) 0.244 4.88 18" to 24" 2047.1 1 26" to 36" 1206.2 0 5.8 Flexibles All 404.1 2 8.91 49.5

Rev 0

Upper bound 22.8 20 45.8 23.2 24.9 156

Note 6.1: [1] assesses that statistically the following factors have no significant effect on the recorded frequency of loss of containment from steel risers; length of pipeline that the riser is attached to, riser diameter, riser contents, location of riser internal or external steel jacket. However, see section 2.1.4 for discussion of effects for different parameters. Note 6.2: This 18" riser failure is due to the escalation of a major platform fire. 4

Table 7a: Frequency (per 10 pipe-years) of loss of containment caused by anchoring and impact incidents in the platform safety zone (within 500 m of the platform) [1] 5.5a Diameter Experience Number of Lower Best Upper bound (pipe-years) incidents bound estimat e Steel lines 2" to 8" 2334 2 1.54 8.57 27 > 10" 5323.3 4 2.57 7.51 17.2 10" to 16" 2069.4 4 6.62 19.3 44.2 18" to 24" 2047.7 0 3.42 14.7 26" to 36" 1206.2 0 5.8 24.9 Flexibles All 550.8 0 12.7 54.5 Table 7b: Frequency (per 104 pipe-years) of loss of containment caused by anchoring and impact incidents in the subsea well safety zone (within 500 m of the subsea facility) [1] 5.5b Diameter Experience Number of Lower Best Upper (pipe-years) incidents bound estimate bound Steel lines 2" to 8" 841.6 0 8.32 35.6 > 10" 89.3 0 78.4 336 10" to 16" 87 0 80.5 345 18" to 24" 2.3 0 3040 13000 26" to 36" 0 0 Flexibles All 657 3 12.5 45.7 118

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Table 7c: Frequency (per 104 pipe-km-years) of loss of containment caused by anchoring and impact incidents in the mid-line of pipelines [1] 5.5c Diameter Experience Number of Lower Best Upper (pipe-km-years) incidents bound estimate bound Steel lines 2" to 8" 13669.1 3 0.6 2.19 5.67 > 10" 110084.1 1 0.005 0.091 0.431 10" to 16" 15423.4 0 0.454 1.95 18" to 24" 21289.4 1 0.024 0.47 2.23 26" to 36" 73371.3 0 0.095 0.409 Flexibles All 808.8 1 0.618 12.4 58.6 Note 7.1: Frequency of loss of containment caused by anchoring and impact incidents is significantly larger for safety zones than for mid-line. In addition, diameter of pipeline is a significant parameter for incidents in the mid-line. Note 7.2: Protection of lines (unprotected, trenched, buried) and age of pipeline appears to have minor effect on the recorded frequency data. Table 8a: Frequency (per 104 pipe-km-years) of loss of containment caused by corrosion and material defects for pipelines less than 2 km in length Contents Steel lines All Oil Gas Other Flexibles All

Experience (pipe-km-years) 680.6 280.6 254.9 145.1 298.5

Number of incidents 7 6 1 0 5

Lower bound 48.3 93 1.96 66

Best estimate 103 214 39.2 48.2 168

Upper bound 193 422 186 207 352

Table 8b: Frequency (per 104 pipe-km-years) of loss of containment caused by corrosion and material defects for pipelines 2 to 5 km in length Contents Steel lines All Oil Gas Other Flexibles All

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Experience (pipe-km-years) 5034.7 1654.4 2280.8 1099.5 609.3

Number of incidents 3 0 0 3 2

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Lower bound 1.63 7.46 5.91

Best estimate 5.96 4.23 3.07 27.3 32.8

Upper bound 15.4 18.1 13.2 70.5 103

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Table 8c: Frequency (per 104 pipe-km-years) of loss of containment caused by corrosion and material defects for pipelines greater than 5 km in length Contents Steel lines All Oil Gas Other Flexibles All

Experience (pipe-km-years) 122542.4 35026.9 78160.1 9355.4 340.4

Number of incidents 3 3 0 0 0

Lower bound 0.067 0.234 -

Best estimate 0.245 0.856 0.09 0.748 20.6

Upper bound 0.632 2.21 0.384 3.21 88.1

Note 8.1: There is a strong dependency between pipeline length and frequency of loss of containment caused by corrosion and material defects. For longer pipelines a very significant decrease in frequency is observed. For comparison, data on offshore pipelines from the Gulf of Mexico are given in Table 9. Table 9: Frequency (per 104 pipeline-km-years) of pipeline leakage outside platform safety zone (more than 1000 m away from the platform) in Gulf of Mexico [2] ,

Failure mode Anchor/impact Material defect/corrosion Other Total

< 8" 0.21 0.65 0.21 1.1

Pipeline Diameter (inches) 8" to 18" 0.1 0.45 0.09 0.27

> 20" 0.009 0.084 0.014 0.11

Note 9.1: The pipeline population in GoM appears to contain a large proportion of small diameter pipelines, and a substantial part of the pipeline population is old. This factor will tend to make the failure rates rather high compared to the North Sea. 2.1.4 Discussion Failure mechanisms and failure rates of pipelines and risers will depend on a number of technical, operational and environmental parameters. The experience data presented in the previous sections do, to some extent, justify these dependencies with statistical significance. However, a quantification of the influence and importance of all these inherent parameters is not statistically possible due to scarce data samples and limited experience. In order to provide some guidance on these parameters, a qualitative assessment of the effects is given in Table 10. The effects of these parameters may not only relate to the failure rate, but also to other aspects of the failure mechanisms, like the leak hole size distribution, the progression of an initially minor leak etc. Normally, engineering judgement will be applied in order to quantify the effects of specific parameters on failure rate etc.

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Table 10: Indicative effects of different parameters on failure rate and failure mechanisms Failure mode Corrosion (external coating

Effect on failure rate Parameters tending to

Parameter Wet CO2 in carbon steel pipe Riser inside water filled concrete leg

and cathodic

increase

Warm sea

protection

failure rate

Riser clamps in splash zone

Parameters

Sleeving External Inconel 625 overlay

tending

Duplex stainless steel

to decrease

Monel sleeve

failure rate

Inspection

assumed)

Intelligent pigging Age 4 - 20 years ("bathtub" effect) Design (utilisation) factor 0.3 instead of 0.6 Inside dry concrete leg External impact

Parameters

Monel cladding Riser position outside jacket

tending to increase failure rate

Pipelines exposed or trenched Landing position of supply boats on same side as riser

Parameters tending

Riser within crane reach Shipping lane within 5 km of platform Riser position inside jacket/concrete leg

to decrease failure rate

Burial of pipeline Diameter/wall thickness No significant merchant shipping in area Operational restricions in bad weather, defined vessel no-go areas, Agreed approach procedures Fenders/sleeving of risers outside jacket

Failure mode Effect on failure rate Mechanical defects Parameters tending to increase failure rate Parameters tending to decrease failure rate

Natural hazards

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Parameters tending to increase failure rate

Parameter Duplex stainless steel Wall thickness > 25 mm Seamless riser Comprehensive inspection (NDT, etc) Manual inspection Design (utilisation) factor 0,3 instead of 0.6 Riser clamps; redundancy in design, regular inspection, monitoring of riser motion etc. Severe local conditions (earthquakes, hurricanes etc.)

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Riser and Pipeline Leaks

2.2

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Onshore Pipelines

Table 11 presents estimated leakage frequencies for onshore gas and oil pipelines in Western Europe. The references give more detailed information on leak frequency as a function of pipeline diameters, hole sizes, age, wall thickness etc. Table 11: Freq.(per 104 km-years) of leakage from onshore pipelines in Western Europe Failure mode External interference Construction/material defects Corrosion Ground movement (incl. flooding) Other (incl. operator error) Total

Gas pipeline [4] 1970-92 1988-92 0.3 0.22 0.11 0.07 0.08 0.05 0.03 0.02 0.06 0.02 0.58 0.38

Oil pipeline [3] 1984-88 0.17 0.14 0.17 0.02 0.08 0.58

Note 11.1: The data on oil pipeline leaks [3] includes 51 incidents from a total of 17700 km of pipelines operated or owned by the 63 members of CONCAWE. The population includes pipelines of all sizes carrying both crude oil and products. Of the 51 incidents, 37 caused spill of less than 10 m3 net volume, 5 leaks from 11-100 m3, 8 leaks from 101-1000 m3 and 1 spill of more than 1000 m3. Net volume is the estimated or measured gross spillage minus the volume of oil recovered. Note 11.2: The total length of the gas pipeline system of the eight major gas transmission system operators comprising EGIG is 92853 km. The exposure in the period 1970-92 is 1.47 million km-years. Almost 50% of the exposed pipeline system is in the 5"-16" range and 20% has a diameter of more than 30". Note 11.3: The discussion on effect of different parameters in section 2.1.4 is also valid for onshore pipelines. Reference [6] presents data on leaks from onshore pipelines in the US. Accident statistics is compiled by the US Department of Transportation (DoT) for all pipelines that involve explosion or fire, the loss of 50 bbl or more of liquid, the loss of 5 or more bbl of highly volatile liquid, the death or bodily harm to any person or estimated property damage exceeding $5000. During the studied period from 1982 to 1991, the DoT regulated an average of 344575 km (214155 miles) of liquid pipeline per year. Table 12 gives the failure rate by the various causes. Table 12: Pipeline failure rates by cause for onshore US pipelines (1982-1991) [6] Accident cause Number of accidents Failure rate (per 104 km-years) Outside force 581 1.69 Corrosion 523 1.52 Other 496 1.44 Operator error 107 0.31 Pipe defect 98 0.28 Weld defect 54 0.16 Relief equipment 42 0.12 Total 1,901 5.52 Table 13: Pipeline failure rates by cause for subcategories of the outside force category1 [6] 13/06/2003

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Outside Force Breakdown 10 yr accident total Damage by others 265 Damage by operator 43 Natural forces 20 Other outside force 18 Ship anchor 4 Washout 3 Landslide 2 Subsidence 2 Frostheave 2 Fishing operation 2 Earthquake 0 Mudslide 0 1 For accidents that occurred between 1986 to 1991

Rev 0

Failure rate (per 104 km-years) 1.28 0.21 0.1 0.09 0.02 0.01 0.01 0.01 0.01 0.01 0 0

Note 12.1: Figures in italics denote accidents that occured between 1986 to 1991. 2.3

Ignition Probability

There will be a large number of parameters that influence the probability of ignition of a release from a riser or pipeline leakage. The data in Table 14 splits the estimates on leakage size and location of release. Table 14: Probability of ignition of a hydrocarbon release from a riser leakage [5] Typical probability of ignition (integrated platform) Location of release Massive gas Major gas Minor gas release (20 kg/s) release (2-20 kg/s) Riser above sea 0.168 0.026 0.005 Subsea 0.443 0.13 0.043 Typical probability of ignition (bridge linked complex) Location of release Massive gas Major gas Minor gas release (20 kg/s) release (2-20 kg/s) Riser above sea 0.078 0.013 0.002 Subsea 0.14 0.051 0.002 Typical probability of oil releases (calculate flash gas and treat as gas release) Location of release Massive oil Major oil release Minor oil release (20 kg/s) (2-20 kg/s) Riser above sea 0.051 0.009 0.003 Subsea 0.005 0.001 Note 14.1: The ignition probabilities quoted in Table 14 are from a study that included development of a model relating probability of ignition to the size of release, its location and other relevant factors. Table 15: Historical ignition probability for onshore gas pipelines (1970-92) [4] 13/06/2003

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Riser and Pipeline Leaks

Damage classification Pinhole/crack Hole Rupture (16 °API)

55

Heavy Crude Oil (5 miles from airport < 5 miles from airport

3 x 10-9/well-year -6 6.6 x 10 /well year

Derrick collapse: Because of the relatively close spacing (60 to 120ft) of wellheads on the pads in the Kuparuk field, a blowout frequency due to derrick collapse was determined. The derrick collapse failure rate (one rig collapse per 4,000 rig years) was determined based on historical data from rigs companies. Derrick collapse

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-5

1 x 10 /well year

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The reader should note that the ‘Mechanical Lifting Failures - Dropped Objects’ datasheet, indicates that the failure rate for an offshore derrick structure is 3.4 x 10-5, an order of magnitude difference on the above. 3.5

Onshore - ERCB Database

Whilst all the information needed to derive blowout frequencies is available, the authors are not aware of any publicly available analysis. Table 21: Onshore Texas Blowout Data [5] (1970-1992) Year 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 TOTAL

Wells 7802 7487 8073 8380 9888 12874 12286 14451 15145 14994 19173 25465 24615 23181 26417 23029 12830 10887 9383 7970 7086 8690 7462 317568

Blowouts 7 3 3 7 12 9 8 12 27 27 38 33 24 18 23 25 15 11 7 4 13 6 4 336

Table 22: Historical Onshore Texas Blowout Probability [5] (1970-1992) Total Onshore Texas Year No. of Wells No. of Blowouts Wells/Blowout Probability

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70-92 317568 336 945 0.0011

70-79 111380 115 969 0.001

BLOWOUTS.DOC

80-92 206188 221 933 0.0011

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REFERENCES [1]

"Blowout Risk Modelling", ASME Paper No. OMAE-95-1332, December 1994.

[2]

"Accidents Associated with Oil and Gas Operations, Outer Continental Shelf 19561990" MM5 92-0058, US Department of the Interior, Minerals Management Service, October 1992.

[3]

Minerals Management Service, OCS Report MMS 88-001

[4]

"Subsurface Safety Valves: Safety Liability", J M Busch, et al, Journal of Petroleum Technology, pp1813 - 1818, October 1985.

[5]

Texas Railroad Commission Reports

[6]

API Petroleum Data Book (1993)

[7]

"World Offshore Accident Database". DNV Technica Norge, PO Box 300, N-1322 Hovek, Norway.

[8]

"SINTEF Offshore Blowout Database". Trondheim, Norway.

[9]

“Hydrocarbon Leak and Ignition Database”, E&P Forum, 1992.

13/06/2003

BLOWOUTS.DOC

SINTEF Safety and Reliability, 7034

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MECHANICAL LIFTING FAILURES DROPPED OBJECTS

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DROPPOBJ.DOC

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TABLE OF CONTENTS

1.

SUMMARY -------------------------------------------------------------------------------------------- 3 1.1 Scope--------------------------------------------------------------------------------------------------------------------------3 1.2 Application ------------------------------------------------------------------------------------------------------------------3

2.

KEY DATA---------------------------------------------------------------------------------------------- 3

REFERENCES-------------------------------------------------------------------------------------------- 12

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1. 1.1

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SUMMARY Scope

This data sheet gives information about incidents resulting from the unsafe use or failure of cranes and other lifting devices. Specifically, it focuses on dropped object and swinging load accidents that could lead to the release of hydrocarbon, the damage of assets, or the physical harm of personnel. 1.2

Application

The datasheet provides dropped load frequencies. In practice, risk assessments also consider other numerical inputs apart from purely dropped load frequency. For example, probabilities are often applied to account for other case-specific factors even though there may be no published data available. Some examples of these factors are: • • • •

Crane loading distribution including consideration of number of lifts per week and the time duration of the lifts Probability of hydrocarbon release and ignition upon impact Probability of target impact: pipework, structure, equipment Probability of deck penetration

2. KEY DATA Serious Incidents Due to Dropped Objects and Swinging Loads (UK North Sea) Table 1 is the result of a study performed by the Health & Safety Executive on incidents surrounding lifting and rigging operations. The values in Table 1 were obtained from the Department of Energy/HSE ‘Safety’ database (Reference 1) on all recorded incidents involving cranes over the period 1981 to the end of September 1992. Records are based on incidents reported under the OIR9A reporting scheme. The database contained details of some 1160 incidents. Many of the incidents were of a relatively minor nature. Consequently the data was analyzed by the HSE to identify more “serious” incidents where it was believed that the potential existed for escalation into a significant event involving death or serious injury. Therefore, the analysis inevitably involved a degree of subjectivity as to which incidents had the potential to escalate to a “serious” incident. In many cases this issue was fairly clear-cut. In order to calculate incident frequencies on a per installation year basis, details of the number of installations (fixed and mobile) operating in each of the years was also required. Information for the years 1981 to 1990 were taken from the Department of Energy ‘Brown Book’. However, due to a change in format, the ‘Brown Book’ does not give equivalent figures for 1991 and 1992 and estimates had to be made for those years. The frequencies are calculated on a ‘per installation year’ basis.

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Incidents classed as “serious” were further sub-divided into incidents where: a. b. c.

impact was on the installation itself the dropped object fell into the sea (and hence could have impacted subsea equipment) the impact occured on a supply vessel

Incidents were further sub-divided by the type of lifting device involved. The types considered were: a. installation main cranes (pedestal cranes) b. derrick cranes (It is believed this category included crane barges working at or near an installation. An accident on a crane barge in transit is not believed to be included.) c. other fixed lifting devices e.g., lifting beams (including trolley cranes/hoists) d. portable lifting devices (e.g., chain blocks/slings etc.)

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Table 1: Serious Dropped Objects and Swinging Load Incidents (UK North Sea) [1] (Includes Fixed Installations, Jackups, Semi-subs) Year

Inst’n Year

Main Cranes

Derrick Cranes

Other Fixed Cranes

Impact

Freq

Fall

Freq

Impact

Freq

Impact

Freq

Fall

Freq

on

per

to

per

on

per

on

per

to

per

on

Inst’n

Year

Sea

Year

Vessel

Year

Inst’n

Year

Sea

Year

1

0.011

81

89

6

0.067

6

0.067

4

0.045

82

97

6

0.061

9

0.093

4

0.041

83

108

7

0.065

3

0.028

2

0.018

84

133

11

0.082

4

0.030

10

0.075

85

140

5

0.036

3

0.021

3

0.021

86

145

4

0.027

5

0.034

3

0.020

2

0.014

87

138

9

0.065

2

0.014

3

0.022

2

0.013

88

182

6

0.033

3

0.016

2

0.011

4

0.022

89

191

6

0.031

3

0.016

3

0.016

1

0.005

90

200

4

0.019

1

0.005

3

0.015

3

0.015

91

200(a)

10

0.050

2

0.010

1

0.005

2

0.010

92

150(a)

5

0.033

3

0.020

3

0.020

SUM

1777

79

0.044

44

0.025

41

0.023

2

0.018

5

0.051

1

0.009

1

17

0.010

1

Impact Freq

Total

Avg. Freq.

Fall

Freq

Impact

Freq

Fall

Freq

No.

per

per

to

per

on

per

to

per

of

installation

Inst’n

Year

Sea

Year

Inst’n

Year

Sea

Year

Inc.

year

3

0.034

1

0.011

21

0.236

3

0.031

28

0.289

22

0.204

29

0.218

12

0.086

1

0.010

1

0.009

5

0.046

1

0.007

3

0.022

1

0.009

0.007

0.007 3

1

Portable Devices

0.016

0.005

1

0.005

1

0.007

3

0.020

10

0.006

12

0.007

1

n/a

1

0.007

15

0.103

1

0.007

18

0.130

5

0.027

23

0.280

1

0.005

15

0.078

1

0.005

12

0.059

16

0.080

16

0.107

227

0.128

1

0.007

22

0.012

1

n/a

Notes: (a) Estimates. INCIDENTS:

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TOTAL TO INSTALLATION = 130 TOTAL TO SEA = 56 TOTAL TO VESSEL = 41 AVERAGE INCIDENTS PER YEAR, ‘81 - ‘86 = 21 AVERAGE INCIDENTS PER YEAR, ‘87 - ‘92 = 17

DROPPOBJ.DOC

AVG. FREQ. = 0.073 per installation year AVG. FREQ. = 0.031 per installation year AVG. FREQ. = 0.023 per installation year AVG. FREQ. = 0.19 per installation year AVG. FREQ. = 0.10 per installation year

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Frequency of Major Mechanical Failures of Secondary Structures (Worldwide, ‘70-’94) The data provided in Tables 2-4 are from WOAD (Reference 2) and an E&P Forum member source [3]. The types of failures which are considered in Table 2 are catastrophic failures which could be the top events in a risk assessment. Blowouts and fires in drilling facilities that lead to derrick collapse are not included. For the frequency of derrick failures presented in Table 2, no specific data were found on structural failures. However, since both crane towers and derricks are tall structures supporting irregular loads, it is proposed that the failure frequency for crane towers could be applied to derrick structures. Reference [3] indicates that the failure rate of a crane tower is 18% of the total failure rate for cranes. Applying this proportion to the WOAD historical rate for severe plus significant damage on a fixed platform of 0.187 x 10-3 /Unit yr, a failure rate for the tower would be 0.034 x 10-3 /Unit yr. Therefore, rate proposed for failure of a derrick is 0.034 x 10-3 /Unit yr. Table 2: Frequency of Major Mechanical Failures of Secondary Struct. (Worldwide,’70-’94) Secondary Structure Crane

Derrick

Frequency of Failure (x10-3/Unit yr) 0.187 [2]

0.034 [3]

Included Tower or jib collapse. Total failure of lifting devices during lifting

Collapse of derrick structure

Not Included Noncatastrophic failure of mechanical component Blowout or fire in drilling facilities

Freq. of Structural Damage per Unit Year Due to Crane Accidents (Worldwide, ‘70-’94) Data presented in Table 3 comes from the WOAD databank [2] which provides information on crane accidents as a separate category. The frequencies of severe and significant structural damage due to crane accidents are given. It is not clear whether or not the data in Table 3 includes crane barges. The definition of Severe and Significant Structural Damage as given in WOAD is: • •

Severe structural damage implies serious damage to several modules of the unit. In the case of mobile units this damage can hardly be repaired on site. The cost of damage is typically above 2 million USD. Significant structural damage implies serious damage to module, local area of unit, or minor structural damage to the unit itself. The cost of the damage is typically in the range of 0.9-2 million USD.

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Table 3: Number of Accidents and Frequency of Structural Damage per Unit Year due to Crane Accidents (Worldwide, ‘70 - ‘94) [2] Type of Unit Accident Severity

No. of Accidents Installation Years Frequency (10-3/Unit yr)

Severe

Fixed Units Significant

1 0.01

17 96,255 0.177

Total

Severe

18

2

0.187

0.186

Mobile Units Significant

22 10,781 2.04

Total

24 2.23

All (Fixed + Mobile) 42 107,136 0.39

Types of Crane Accidents and Estimated Frequencies (Worldwide, ‘70-’94) Reference [3] provides annual rates for crane accidents (including crane falls, boom falls, and load falls) on a floating production platform. However, these frequencies are high compared to those derived from WOAD in Table 3. Nevertheless, the distribution (i.e., percentages) between different types of crane accident may be helpful in risk analysis. Therefore, the suggested distribution in Reference 3 has been applied to the WOAD figures given in Table 3 to produce the breakdown in Table 4. Table 4: Types of Crane Accidents and Estimated Frequencies (Worldwide, ‘70-’94) Type of Accident Crane Fall Boom Fall Load Fall All (Ref. 2)

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% Distribution (Reference 3) 19% 54% 27% 100%

Frequencies (x10-3/ Unit yr) Fixed Units Mobile Units 0.036 0.42 0.101 1.21 0.050 0.60 0.187 2.23

DROPPOBJ.DOC

All 0.07 0.21 0.11 0.39

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Reported Failures Rates for Cranes on Fixed Platforms in the UK Sector of the North Sea Information found in Tables 5 and 7 comes from two sources. The first by DEn [4] is a compilation of descriptions of accidents in the UK sector of the North Sea. The second by Noble Denton [5] provides recommendations for potential developments in the North Sea. The values in Table 5 are from DEn accident reports for the UK sector of the North Sea. They include a large number of non-injury incidents, described as DIs. The data is entered in two ways; classified by type of incident (DI, SA, or FA) and by cause (EF, LH, FI, or OT). The population of cranes in the UK sector of the North Sea [5] was obtained and converted to crane years using the year when production started for each installation. Crane years for installations starting production in a year are included in the exposure for that year, assuming that platform cranes will be extensively used during commissioning and drilling. Table 5a Base Data for the Dervication of Frequencies [5]: Year 1980 1981 1982 1983 1984

Platform Population 116 122 126 138 156

Year

Platform Population

1985 1986 1987 1988 Total Platform Years

167 172 180 192 1369

Table 5b: Reported Failure Rates for Cranes on Fixed Platforms in the UK North Sea [4,5] Failure Code

Description

Number of Incidents

Failure Rate 1 (x10-6/hr)

Equipment Failure Lifting/handling Fire Other Failures

121 40 3 8

11.1 3.7 0.3 0.7

Dangerous Incidents Serious Accidents Fatal Accidents

157 14 1

14.3 1.3 0.1

Cause EF LH FI OT Incident Type DI SA FA 1

The Failure Rate (or frequency) was determined as shown below using the crane population data from [6].

For example: Failure Rate for EF Total Crane Years = 1369 x 2 = 2738 (Assuming 2 cranes/platform) Assuming 4000 hr/year of crane operation, Time in service = 2738 x 4000 = 10.95 x 106 hours of crane operation. Failure Rate for EF = 121/(10.95x106) = 11 x 10-6 /hr of crane operation. The UK Department of Energy defines a Serious Accident as one that involves injury to person(s), whereas, a Dangerous Incident is a “near-miss” incident.

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Failure Rate of Diesel Hydraulic Driven Cranes Table 6 gives the failure rate for dropped loads for diesel hydraulic driven cranes used on offshore platforms. The majority of offshore cranes are of this type. The data in Table 6 was obtained from [6] which only covers a small proportion of the total population, yet is the only data source known. Table 6: Failure Rate for Diesel Hydraulic Driven Cranes Failure Mode Load Droppage

Failure Rate (per 106 hours) 11

The data in Table 6 were based on a population of 21 cranes on 20 different installations. UK North Sea Crane Accident Data by Severity and Cause The values in Table 7 are provided by the UK DEn [4] and summarize the accidents in the UK sector of the North Sea. These are available for the period 1981-mid 1985. An analysis has been done of all reports involving cranes, differentiating between fatal accidents, serious accidents and dangerous incidents. Table 7: UK North Sea Crane Accident Data by Severity and Cause [4] Installation Year Type 1981 Fixed Mobile 1982 Fixed Mobile 1983 Fixed Mobile 1984 Fixed Mobile 1985 Fixed (part) Mobile Total Fixed Mobile All

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Number of Incidents (Severity) TOT DI SA FA 22 21 1 0 7 7 0 0 50 48 2 0 3 3 0 0 22 18 3 1 17 12 5 0 55 50 5 0 11 10 1 0 23 20 3 0 3 3 0 0 172 157 14 1 41 35 6 0 213 192 20 1

Number of Incidents (Causes) EF LH OT FI 15 4 3 0 6 1 0 0 39 6 3 2 3 0 0 0 15 7 0 0 10 7 0 0 32 20 2 1 6 5 0 0 20 3 0 0 3 0 0 0 121 40 8 3 28 13 0 0 149 53 8 3

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Relative Breakdown of Crane Accidents by Severity (UK North Sea) Table 8 below gives a relative breakdown of crane accidents by severity for the UK North Sea for the period from 1980 to 1990. These crane accidents include both fixed and mobile installations. This information was obtained from the UK Department of Energy “Brown Book” [7], and differs only slightly from that in Table 7 for the years 1981 through 1984. However, no breakdown of the incidents by cause is available from this reference. Table 8: UK North Sea Crane Accident Data by Severity 1980 - 1990 [7] Number of Incidents (Severity)

Total

Year

FA

SA

DI

Incidents

1980

1

4

32

37

1981

0

1

29

30

1982

0

3

50

53

1983

1

6

32

39

1984

0

6

62

68

1985

0

8

52

60

1986

2

6

48

56

1987

0

0

20

20

1988

3

1

25

29

1989

0

2

49

51

1990

0

4

37

41

Total

7

41

436

484

Avg ‘80-’90

0.7

4

44

48

Platform Crane and Drilling Rig Derrick Accident Data by Cause (US Gulf of Mexico) The incidents found in Table 9 were taken from the MMS (Reference 8) and summarize offshore oil and gas operation incidents in the Gulf of Mexico between 1956 and 1990. The incidents include structural failures of the crane that resulted in dropped loads (e.g., failure of a chord, crane cab connection, slings) up to total collapse. Populations were taken from reports by the Offshore Oil Scouts Association [9]. However, where data for a given year was not available, the population was determined by interpolating between those years where data was available. Table 9:US Gulf of Mexico Platform Crane & Drilling Rig Accident Data by Cause (1956-‘90) Total Period

‘56-90

Platform Incidents

Totals

Average

Inst’n

No. of

Freq. of

No. of

Freq. of

No. of

Freq. of

No. of

Freq. per

Years

Crane

Crane

Rigging

Rigging

Human

Human

Incidents

Installation

Failures

Failures

Failures

Failures

Errors

Errors

12

4.9E-04

19

7.7E-04

5

2.0E-04

24741

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Total Period

‘56-90 Note:

Rev 0

Drilling Rig Incidents

Totals

Average

Inst’n

No. of

Freq. of

No. of

Freq. of

No. of

Freq. of

No. of

Freq. per

Years

Derrick

Derrick

Rigging

Rigging

Human

Human

Incidents

Installation

Failures

Failures

Failures

Failures

Errors

Errors

2

5.9E-04

18

5.3E-03

1

3.0E-04

3368

Year 21

6.2E-03

All frequencies are on a per installation year basis. Number of failures was determined from Reference 8. The platform population and installation years was determined from [9]

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REFERENCES 1.

J. N. Edmondson and T. Norman, “An Examination of the Number and Frequency of Serious Dropped Object and Swing Load Incidents Involving Cranes and Lifting Devices on Offshore Installations for the Period 1981-1992,” Offshore Technology Report - OTN 93 222, Health & Safety Executive, Sept. 1993.

2.

WOAD - World Offshore Accident Databank, Statistical Report, 1994, Veritec, Norway.

3.

E&P Forum Member, 1985.

4.

UK Department of Energy Accident Summaries, 1981-1985.

5.

Noble Denton North Sea Field Development Guide, through 1988.

6.

OREDA-92 - Offshore Reliability Data, 2nd Edition, DNV Technica.

7.

UK Department of Energy “Brown Book”, 1981-1985.

8. Lloyd M. Tracy, “Accidents Associated with Oil and Gas Operations: Outer Continental Shelf 1956-1990”, US. Department of the Interior, Minerals Management Service, Oct. 1992. 9.

Offshore Oil Scouts Association, “Status of the Offshore Oil Industry & Statistical Review of Events”, Multiple Issues, through 1995.

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SHIP/INSTALLATION COLLISIONS

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Table of Contents

1 INTRODUCTION-------------------------------------------------------------------------------------- 4 2 CATEGORIES OF COLLIDING VESSELS --------------------------------------------------- 5 2.1 Merchant Vessels ------------------------------------------------------------------------------------------------------ 7 2.2 Naval Traffic ----------------------------------------------------------------------------------------------------------- 7 2.2.1 Surface Traffic---------------------------------------------------------------------------------------------------------7 2.2.2 Submerged Submarine Traffic --------------------------------------------------------------------------------------7 2.3 Fishing Vessels --------------------------------------------------------------------------------------------------------- 8 2.4 Offshore Traffic ------------------------------------------------------------------------------------------------------- 8 2.4.1 External Offshore Traffic --------------------------------------------------------------------------------------------8 2.4.2 Field Related Offshore Traffic --------------------------------------------------------------------------------------8

3 HISTORICAL COLLISIONS --------------------------------------------------------------------- 10 3.1 Introduction ---------------------------------------------------------------------------------------------------------- 10 3.2 Passing Vessels ------------------------------------------------------------------------------------------------------- 10 3.2.1 Passing Vessel Collisions UK Continental Shelf -------------------------------------------------------------- 10 3.2.2 Passing Vessel Collisions Norwegian Continental Shelf ----------------------------------------------------- 11 3.2.3 Passing Vessel Collisions Dutch Continental Shelf ----------------------------------------------------------- 12 3.2.4 Passing Vessel Collisions German Sector----------------------------------------------------------------------- 12 3.2.5 Passing Vessel Collisions World Wide-------------------------------------------------------------------------- 12 3.2.6 Evaluation of Data - Passing Vessel Collisions ---------------------------------------------------------------- 13 3.3 Visiting Vessels------------------------------------------------------------------------------------------------------- 14 3.3.1 Introduction ---------------------------------------------------------------------------------------------------------- 14 3.3.2 Operational Exposure - UK Sector ------------------------------------------------------------------------------- 14 3.3.3 Reported Collision Incidents - UK Sector ---------------------------------------------------------------------- 14 3.3.4 Collision Frequency Per Installation-Year - UK Sector ------------------------------------------------------ 15 3.3.5 Collision Frequency Per Vessel Visit ---------------------------------------------------------------------------- 18 3.3.6 Collision Frequency Per Vessel Orientation -------------------------------------------------------------------- 19 3.3.7 Collision Causation Factors - Visiting Vessels----------------------------------------------------------------- 19 3.3.8 Evaluation of Data - Visiting Vessel Collisions---------------------------------------------------------------- 21

4 COLLISION FREQUENCY MODELLING --------------------------------------------------- 23 4.1 Introduction ---------------------------------------------------------------------------------------------------------- 23 4.2 Ship/Installation Collision Frequency Modelling ------------------------------------------------------------- 23 4.2.1 Important Factors Affecting Collision Frequency ------------------------------------------------------------- 23 4.2.2 Collision Frequency Models--------------------------------------------------------------------------------------- 25 4.3 Vessel Traffic Pattern and Volume ------------------------------------------------------------------------------ 25 4.3.1 General---------------------------------------------------------------------------------------------------------------- 25 4.3.2 Factors Affecting the Traffic Volume---------------------------------------------------------------------------- 25 4.3.3 How to get Traffic Data -------------------------------------------------------------------------------------------- 26

5 COLLISION CONSEQUENCES---------------------------------------------------------------- 27 5.1 General ---------------------------------------------------------------------------------------------------------------- 27

6 RISK REDUCING MEASURES----------------------------------------------------------------- 28 13/06/2003

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6.1 Use of Risk Reducing Measures ---------------------------------------------------------------------------------- 28 6.2 Overview of Risk Reducing Measures--------------------------------------------------------------------------- 28

7 RESEARCH AND DEVELOPMENT PROJECTS ----------------------------------------- 29 7.1 Introduction ---------------------------------------------------------------------------------------------------------- 29 7.2 UK Continental Shelf Shipping Traffic Database------------------------------------------------------------- 29 7.3 The Effectiveness of Collision Control & Avoidance Systems ---------------------------------------------- 29 7.4 Comparison of ship-platform collision frequency models. -------------------------------------------------- 30

8 REFERENCES -------------------------------------------------------------------------------------- 31

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INTRODUCTION

This data sheet provides data on ship/installation collision risk in relation to activities within the offshore oil & gas Exploration and Production Industry. The risk related to icebergs are not considered. During the last decade, considerable attention has been given to the risk related to collisions between offshore oil and gas platforms and ships in the North Sea. Several research programs have looked into this problem and considerable steps have been taken to improve the modelling of these problems. Collision risk is highly location dependent due to variation in ship traffic from one location to another. The ship traffic volume and pattern at the specific location should hence be considered with considerable care. This dependency on location also means that use of historical data which are averaged over a large number of different locations, is not possible. Field related offshore traffic involve those vessels which are specifically visiting the unit, and are therefore considered to be less dependent of the location of the platform. This means that there will be smaller variation in the collision frequency from one platform to another, and it is possible to use historical data to a much greater extent than for the other collision types.

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CATEGORIES OF COLLIDING VESSELS

Ship traffic may for this purpose be divided into two groups: •

EXTERNAL: Ship traffic which is not related to the installation being considered, including merchant vessels, fishing vessels, naval vessels etc.

•

FIELD RELATED: Offshore-related traffic which is there to serve the installation being considered, e.g. supply vessels, oil tankers, work vessels etc.

Collisions can be divided into two groups: •

Powered collisions ( Vessel steaming towards the installation )

•

Drifting collisions ( Vessel drifting towards the installation )

Powered collisions will cover situations like navigational/manoeuvring errors (human/technical failures), watch keeping failure, bad visibility/ineffective radar use, etc. A drifting vessel is a vessel which has lost its propulsion or has experienced a progressive failure of anchor lines or towline and is drifting only under the influence of environmental forces. In Table 2.1 the different types of vessels that may collide with the platform are shown.

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Table 2.1

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Categories of Colliding Vessels VESSEL CATEGORIES

TYPE OF TRAFFIC

TRAFFIC CATEGORY

VESSEL CATEGORY

REMARKS

EXTERNAL

Merchant

Merchant ships Cargo, ferries etc.

Commercial traffic passing the area

Naval traffic

Surface vessels

Both war ships and submarines

Submerged vessels

Submerged submarines

Fishing vessels

Fishing vessels

Sub-categorised into vessels in transit and vessels operating in the area

Pleasure

Pleasure vessels

Traffic passing the area

Offshore traffic

Standby boats

Vessels going to and from other fields

Supply vessels

Vessels going to and from other fields

Offshore tankers

Vessels going to and from other fields

Tow

Towing of drilling rigs, flotels, etc.

Standby boats

Dedicated standby boats

Supply vessels

Visiting supply vessels

Working vessels

Special services/support as diving vessels, etc.

Offshore tankers

Shuttle tankers visiting the field

FIELD RELATED

Offshore traffic

Each of the traffic categories are presented in the following sections, with an evaluation of relevant traffic patterns and vessel behaviour. Each traffic type behaves in one of several distinct ways in relation to a platform. This must be considered both when reviewing traffic data and when estimating collision frequency.

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Merchant Vessels

Merchant vessels are frequently found to represent the greatest platform collision hazard, since: • • •

Merchant vessels are often large and may thus represent considerable impact energy. The traffic may be very dense in some areas. No prevailing influence by oil and gas operators.

In addition there is a problem of the uncertainties in the risk estimates which are higher than for many of the other vessel groups as merchant vessel operating standards vary in quality. 2.2

Naval Traffic

Estimating risk associated with naval vessels is a problem because information about movements and volume is restricted and hence difficult to obtain. Estimation very often has to be based on surveys or subjective evaluation. Further, the volume is difficult to assess since possible routes and areas where naval vessels operate/exercise can vary each year. The variation in traffic routes and density can also be dependent on the political situation. Naval traffic may be divided into two main categories, surface traffic (submarines included) and submerged traffic. 2.2.1 Surface Traffic As already mentioned, collisions are either due to drifting of the vessel or may occur while the vessel is under power (errant vessels). Drifting is less likely to happen with a naval vessel than with a merchant vessel because it is designed to operate under difficult conditions and thus with a high degree of reliability. A reduced probability of drifting combined with a relatively low number of vessels usually makes this scenario negligible, at least in relation to the overall collision risk. As regards collisions under power, this scenario can probably also be disregarded. These vessels have a large crew compared to merchant vessels. They will always have at least two persons on the bridge (large vessels like frigates, destroyers, carriers etc. will have more personnel on the bridge). Normally the operation room is also manned. Considering the number of personnel "on watch" it seems very unlikely that a naval surface vessel should not know of/detect the platform and avoid it compared to a merchant vessel. In addition, naval vessels are more likely to operate in groups, something which also will reduce the collision probability. Submarines operating on the surface are not considered to represent any higher threat to the platform than any other surface vessel. All in all, it is considered that the contribution to overall collision risk from such vessels is likely to be very low. 2.2.2 Submerged Submarine Traffic As for naval surface vessels, due to a reduced probability of drifting combined with a relatively low number of vessels, the contribution from drifting submarines to the overall collision risk is neglected. Submerged submarines are in a special situation because they do not have a look-out. Navigation is therefore completely dependent on electronic navigational aids and sonar. 13/06/2003

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A 550 ton, West German submarine collided with Norsk Hydro’s Oseberg B platform in March 1988 causing damage estimated at up to NOK 200 million. In connection with this accident, it was stated that it was often very difficult for submarines to detect platforms which do not emit much sound in the water. In principle submarines are officially restricted from operating in the immediate vicinity of offshore installation in times of peace. Nevertheless the Norsk Hydro incident shows a deviation from this principle. Some data on the submarine traffic have been collected [1]. An appropriate number of submarines in activity in the entire North Sea, at all times, seems to be in the region of 15 25. 2.3

Fishing Vessels

Fishing vessels are divided into two groups, depending on the operational pattern : • •

Fishing vessels can be in transit from the coast to and from different fishing areas. Secondly, the vessels may be fishing in an area. The vessel’s operation and behaviour during fishing ( primarily trawling) will be complex and varied, but usually at low speed and with no preferred heading.

Fishing vessels vary in size from large factory/freezer ships to smaller vessels operating near the coast. Typically, a large fishing vessel will have a displacement around 1000 tons. This implies that the collision energy will be less than 20 MJ. For a typical North Sea installation neither drifting vessels nor vessels under power will normally be able to threaten the integrity of the platform. However, the risers and other relevant equipment will have considerably less impact resistance. Powered as well as drifting fishing vessels will hence be considered and models for these scenarios have been developed. 2.4

Offshore Traffic

2.4.1 External Offshore Traffic Passing offshore vessels, tankers as well as supply, standby and work vessels are in many respects similar to passing merchant vessels, except that such vessel operations tend to be more aware of the offshore installations and also may benefit from EP Operator influence (procedure, training competency, communication etc.). Vessels or installations under tow pose particular problems which should be considered separately [1]. 2.4.2 Field Related Offshore Traffic The most frequent collisions/contacts occur between offshore supply vessels and the platform to which they are delivering supplies. Those impacts generally cause only minor damage, although significant impacts have been reported [2]. It is worth noting that e.g. the Norwegian and the UK criteria for design against vessel impacts have been derived from a probabilistic evaluation of supply vessel impacts [3, 4]. These collisions are therefore to a large degree taken care of in the platform design.

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Generally, collisions with any sort of offshore-related traffic can be more easily controlled because the vessels are operated by the oil companies themselves, and they can impose restrictions on this traffic if it is deemed necessary.

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HISTORICAL COLLISIONS

3.1

Introduction

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The history of collision incidents can provide useful information concerning the nature of collision risk. The historical perspective is reviewed in the following sections. The following sources have been available: 1)

Lloyds’ List Casualty Reports entries - World-wide for offshore structures.

2)

Det Norske Veritas World Offshore Accident Database (WOAD) - World-wide.

3)

UK Health and Safety Executive Incident Reports - UK Sector.

4)

US Coastguard Platform Collision Incident Reports.

5)

Norwegian Petroleum Directorate Accident Database.

While historical reports can provide useful insight into collision data, the figures have to be used with great care. There is no obvious or clear threshold of incident severity for the reporting of collisions and no well defined data source population. The way in which the information is reported and the original purpose can substantially affect the end result. Sources used in this report are No. 2, 3 and 5 listed above. Updated reports from No. 1 and 4 have not been available for this study. 3.2

Passing Vessels

3.2.1 Passing Vessel Collisions UK Continental Shelf A report by the UK Health and Safety Executive (HSE) [5] identifies the following major collision incidents during the period from 1973 through 1993. Table 3.1 Year 1988 1985 1983 1967*

Passing Vessel Collisions UK Continental Shelf [5] Installation type Jack Up Fixed installation Fixed installation Semi-submersible

Vessel type Merchant Vessel Supply Vessel Merchant Vessel Merchant Vessel

Damage Severe Severe Severe Severe

* This incident is taken from the same reference as the other three incidents, even though it is not part of the time span from 1973 through 1993. It has to be noted that none of these incidents have resulted in major structural collapse or fatalities. Appendix 1 gives a description of the collisions occurred. In addition to these 4 collisions the UK-HSE has recorded in the order of 7 collisions in the same period with minor or moderate damage. The UK-HSE is in the process of updating their internal database. 13/06/2003

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From the same report the following frequencies for severe collisions for the period from 1965 through 1988 are given: Table 3.2

Passing Vessel Collision Frequencies - UK Continental Shelf [5]

Category

Period No. of considered incidents

Fixed (severe incidents) 1965-1988 Mobile (severe 1965-1988 incidents)

2 2

No. of Collision Frequency installation- per installation-year years 1180 1.7 10-3 530 3.8 10-3

The following incidents have been identified with use of WOAD [6], covering the period from 1970 to 1995: Table 3.3

Passing Vessel Collisions - UK Continental Shelf [6]

Year 1995

Installation type Jacket

Vessel type Fishing

1995

Semi-submersible

Merchant

1990

Semi-submersible

Semi-subm.

1988 1984 1983 1976

Jack-up Jack-up Jacket Semi-submersible

Merchant Merchant Merchant Fishing

Damage No collision - evacuation due to drifting vessel No collision - evacuation due to drifting vessel No collision - evacuation due to drifting vessel Severely damaged Insignificant damage (only damage to vessel) Minor damage Damaged (columns)

3 of these incidents have been reported by the UK-HSE (Ref. Table 3.1) as severe incidents (1976, 1983 and 1988). Based on the number of platforms years given for the period 1970-1992 in [8] the following average annual collision frequencies are estimated. Table 3.4 Passing Vessel Collision Frequencies - UK Continental Shelf [6,8] Category

Period considered

Fixed (severe incidents) Mobile (severe incidents)

1970-1992 1970-1992

No. of No. of incidents installation -years 1700 [8] 1 [6] 704 [8] 2 [6]

Collision Frequency per installation-year 5.9 10-4 2.8 10-3

3.2.2 Passing Vessel Collisions Norwegian Continental Shelf Only one collision has occurred on the Norwegian Continental Shelf with external traffic [7]. This was a submarine colliding with the Oseberg platform in 1988 (See Appendix 1). Based on the number of installations years given from [7] for the period 1982 to 1994 are the following historical collision frequency for the Norwegian Continental Shelf estimated. Table 3.5 Category 13/06/2003

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1 [7]

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years 880 [7]

1.1 10-3

3.2.3 Passing Vessel Collisions Dutch Continental Shelf One ship/platform collision has occurred on the Dutch Continental Shelf since 1970. A jacket was in 1988 hit by a drifting ship. This caused however only minor damage [6]. From the on-going research project presented in Section 7.4 the number of installations years is estimated at 1200 for the period 1976 to 1995. Based in this, the following historical collision frequencies are estimated for the Dutch Continental Shelf. Table 3.6

Passing Vessel Collision Frequencies - Dutch Continental Shelf

Category

Period No. of considered incidents

Fixed

1976-1995

1 [6]

No. of installationyears 1200

Collision Frequency per installation-year 8.3 10-4

3.2.4 Passing Vessel Collisions German Sector In September 1995 a German coaster hit the platform H-7. Only limited damage was observed on the platform (minor dents, paint damage). The German vessel, was undamaged except for a broken mast (Ref. Appendix 1). From the on-going research project presented in Section 7.4 is the number of installations years estimated to 70 up to 1995. Based in this, the following historical collision frequency are estimated for the German Sector. Table 3.7

Passing Vessel Collision Frequencies - German Sector

Category

Period No. of considered incidents

Fixed

- 1995

1

No. of Collision Frequency installation- per installation-year years 70 1.4 10-2

3.2.5 Passing Vessel Collisions World Wide A report by the UK-HSE [5] gives the following number of severe collisions for the period from 1965 through 1988: Table 3.8

Passing Vessel Collisions - World wide [5]

Category

Period No. of considered incidents

Fixed (severe incidents) Mobile (severe incidents)

1965-1988 1965-1988

26 6

No. of Collision Frequency installation- per installation-year years 61000 4.3 10-4 8000 7.5 10-4

The following comparable collision frequencies are presented in [8]. Table 3.9 Category

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Passing Vessel Collisions - World wide [8] Period No. of No. of considered incidents installation -years Collisions.doc

Collision Frequency per installation-year

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Fixed (severe incidents) Mobile (severe incidents)

1970-1992 1970-1992

34 5

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89000 9000

3.8 10-4 5.6 10-4

3.2.6 Evaluation of Data - Passing Vessel Collisions The following table summarises the frequencies for severe incidents presented in the earlier sections. Table 3.10

Passing Vessel Collisions -Summary

Area considered

Category

UK Sector UK Sector UK Sector UK Sector Worldwide Worldwide Worldwide Worldwide

Fixed (severe incidents) Mobile (severe incidents) Fixed (severe incidents) Mobile (severe incidents) Fixed (severe incidents) Mobile (severe incidents) Fixed (severe incidents) Mobile (severe incidents)

Collision Frequency per install.year 1.7 10-3 3.8 10-3 5.9 10-4 2.8 10-3 4.3 10-4 7.5 10-4 3.8 10-4 5.6 10-4

References

HSE [5] HSE [5] WOAD [6]/MTD[8] WOAD [6]/MTD[8] HSE [5] HSE [5] MTD [8] MTD [8]

The frequencies presented for passing vessel collisions are in general questionable and sensitive due to the limited statistical data available. For fixed installations the frequencies of severe incidents vary between 3.8 10-4 and 1.7 10-3 per year. For mobile installations the range is 5.6 10-4 to 3.8 10-3 per year. The reporting threshold is seen to be very important. The Lloyds’ List reports and to some extent WOAD, originate primarily for insurance purposes. The damage threshold for a report to occur is therefore likely to be a level of damage sufficient to call in a surveyor. This is indicated by Section 3.2.1 which shows that WOAD compared to the UK-HSE Incident Reports has not recorded collisions with minor or negligible consequences. A certain under estimation of the collision frequencies is also expected on basis of WOAD for severe incidents in the UK Sector. It should however be noted that one minor incident in WOAD seems not to be included in the UK-HSE database. These figures are of course only indicative of the average risk level and cannot be used directly in estimation of risk to one particular installation because there will be very large variations in traffic density. Nevertheless, the relatively high historical risk level indicates that collision risk is a concern that must be taken seriously.

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Visiting Vessels

3.3.1 Introduction Collisions between visiting vessels and offshore installations are relatively frequent occurrences, since these vessels, by definition, must come close to the installation. The most common type of vessel, visiting an offshore installation, is a supply vessel and as a result of this, and the fact that they must maintain close proximity to the installation during on/offloading, the number of supply vessel collisions is higher than for any other type of visiting vessel. Although visiting vessel collisions are relatively frequent, the vast majority of the collisions are of low energy (i.e. bumps against the installations) and cause little more than damaged paintwork and minor denting. This section reviews and discusses the extensive amount of visiting vessel collision data which has been collected for the UK and the Norwegian sectors of the North Sea, and then goes on to estimate the frequency of collision and the likely level of energy which the installation will absorb. An extensive amount of visiting vessel collision data have been collected for the UK and the Norwegian Continental Shelf. Statistics from other parts of the world are considered to be too unreliable when it comes to minor damage and are hence not presented. 3.3.2 Operational Exposure - UK Sector The J.P.Kenny report detailed the operating exposure, measured in installation-years, for installations in the UK sector of the North Sea. During the period from 1975 to 1985, a total installation exposure of 1024 installation-years was estimated. A breakdown of this total is presented in Figure 3-1. 800 Installation-Years

606 600 400

257

200

65

96

Fixed Concrete

Jack-up

0 Fixed Steel

Semisubmersible

Installation Type

Figure 3-1 Operational Exposure in UK Sector of North Sea (1975 - 1985) 3.3.3 Reported Collision Incidents - UK Sector A total of 145 collisions between installations and other vessels were reported to the UK Department of Energy (D.En.) during the period 1975-1985. Not included in this total is one collision which occurred between a tanker and a loading buoy. A breakdown of reported collisions, by type of installation impacted, is presented in Figure 32. From this figure it can be seen that the majority of reported collisions occurred with fixed steel installations and semi-submersible units. 13/06/2003

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No. Of Collisions

100 80

74 54

60 40 7

10

Fixed Concrete

Jack-up

20 0 Fixed Steel

Semisubmersible

Installation Type

Figure 3-2 Number of Reported Collisions by Installation Type in UK (1975 - 1985) The reported collisions were also broken down by type of vessel involved in the collision. This breakdown is presented in Figure 3-3. From this figure, it can be seen that the majority of collisions occurred with supply boats (67% of total). 97

No. Of Collisions

100 80 60 40 20

21

14

5

8

Passing Vessels

Others

0 Standby Vessel

Supply Vessel

DSV Colliding Ve sse l

Figure 3-3 1985)

Number of Reported Collisions by Colliding Vessel Type in UK (1975 -

3.3.4 Collision Frequency Per Installation-Year - UK Sector Based on the data presented in the previous two sections, the frequency of collisions can be determined for an average installation-year of exposure. This is presented in Figure 3-4. It should be noted that, as this section assesses the risks associated with visiting vessels, the five reported collisions from passing vessels (see Figure 3-3) have been excluded from the visiting vessel frequency assessment.

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Collision Frequency per Installation Year

0.25 0.21 0.20 0.15

0.14 0.12

0.11

0.09

0.10 0.05 0.00

Fixed Steel

Fixed Concrete

Jack-up

Semisubmersible

Average

Figure 3-4 Visiting Vessel Collision Frequency by Installation Type (1975-1985) (UK) From Figure 3-4 it can be determined that the visiting vessel collision frequency for semisubmersibles (i.e. 0.21 per installation-year or a collision return period of 4.8 years) is approximately 76% higher than that for a fixed steel installation (i.e. 0.12 per installation-year or a collision return period of 8.5 years). The most probable reason for the variation in visiting vessel collision frequency between semi-submersibles and fixed steel installations is due to the installation exposure values used for the different types on installation. For the fixed steel jackets, the operating experience is in the region of 606 installation-years, with 406 of these being associated with platforms in the Southern North Sea. In the Southern North Sea, there are a number of complexes which have 3-5 bridge linked platforms. Some of these platforms are very rarely, if at all, visited by surface vessels, and in addition there are a large number of Normally Unattended Installations (NUIs) where very few vessel visits are made per year. The exposure for fixed steel jackets, relevant for visiting vessel collision frequency assessment, will therefore be significantly less than the 606 installation-years used, however, without performing a very detailed study of all installations in the North Sea a more appropriate value cannot be obtained. Semi-submersible units, on the other hand, are always manned and visited. The installationyears of semi-submersible exposure are therefore directly relevant for visiting vessel collision frequency assessment. The fact that a semi-submersible moves, due to environmental loads and flexible moorings, is unlikely to have a significant effect on the likelihood of a collision with a vessel in close proximity (e.g. an unloading supply vessel). This is because weather operating criteria during normal operations, when a vessel may be in close proximity, should ensure that environmental loads are not high (i.e. no close proximity work in bad weather). The movement of the semi-submersible is therefore likely to be small and predictable. Any collision, as a result of semi-submersible movement, is likely to be of low energy, with damage to paint-work being the likely consequence. Such minor bumps against the installation may not even have been reported. To obtain a reliable breakdown of collision frequency by type of colliding vessel, the collision frequencies associated with vessels visiting semi-submersible units was assessed. By restricting the installation type to semi-submersibles, the complication associated with multiple platform complexes and NUIs can be avoided. In addition, due to the limited operating exposure of fixed concrete platforms and jack-up mobile units, these types of installation have also been excluded as there would be large uncertainties regarding the calculation of collision frequencies. 13/06/2003

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Of the 54 collisions with semi-submersibles documented in the J.P.Kenny report, 53 were associated with visiting vessels. The remaining 1 was associated with a passing vessel and has therefore been excluded from this assessment. It was also noted in the J.P.Kenny report, that out of the 53 collisions which were associated with visiting vessels, 49 were with supply vessels, 1 with a Diving Support Vessel (DSV), 2 with standby vessels and 1 with an anchor handling tug (AHT). This breakdown of semisubmersible collisions is presented graphically in Figure 3-5.

DSV 2% Standby Vessel 4% AHT 2% Supply Vessel 92%

Figure 3-5 Percentage Breakdown of Semi-Submersible Collisions in UK (1975-1985) Based on the semi-submersible exposure of 257 installation-years, the collision frequency by type of visiting vessel can be determined. This is presented in Figure 3-6.

Collision Frequency per Installation Year

0.20

1.9E-01

0.15

0.10

0.05 3.9E-03

7.8E-03

3.9E-03

DSV

Standby Vessel

AHT

0.00

Supply Vessel

Figure 3-6 Visiting Vessel Collision Frequency for Semi-submersible Units by Colliding Vessel type per Installation-year. From Figure 3-6 it can be seen that the risk of a collision with a semi-submersible, during a year of operation, from a visiting supply vessel is over 12 times higher than the sum of the other vessel types. A frequency of 0.19 per installation-year is equivalent to a collision return period of 5.2 years.

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3.3.5 Collision Frequency Per Vessel Visit During the time that the J.P.Kenny analysis was carried out, a detailed evaluation of the number of vessels visiting a MODU was carried out in the Risk Assessment of Buoyancy Loss (RABL) studies [9]. In this study it was determined that on average the number of visits made to a semi-submersible was approximately 5 per week (based on exploration and appraisal drilling in the Norwegian sector). This number of visits per week includes supply vessels, anchor handling at the beginning of the semi's work and standby vessel changeout once every 28 days. Figure 3-7 presents the average number of vessel visits to a semi-submersible unit for an installation-year.

No. Of Visits (per Installation-Year)

180

176.5

150 120 90

59

60 30 0 Supply Vessel

Unknown (not listed)

22.5

DSV

Standby Vessel

AHT

Colliding Vessel Type

Figure 3-7 Average Number of Visits to a Semi-Submersible Unit per Installation-Year The RABL study did not quantify the average number of DSV visits to an installation, however, it is considered reasonable to assume that on average a DSV would visit a fixed installation once every two years to perform inspection and/or repairs. Based on the collision frequency per semi-submersible installation-year and the average annual number of vessel visits, the collision frequency per vessel visit can be determined and is presented in Figure 3-8.

Collision Frequency per Installation Year

1.0E-02 7.8E-03 7.5E-03

5.0E-03

2.5E-03

1.1E-03

8.0E-04

3.5E-04

6.6E-05

Standby Vessel

AHT

0.0E+00

Supply Vessel

Figure 3-8

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DSV

Average

Visiting Vessel Collision Frequency for Semi-Submersible Units by Colliding Vessel Type per Vessel Visit (1975-1985) (UK Sector) Collisions.doc

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Figure 3-8 it can be seen that the likelihood of collision between a DSV and an installation is 7.8x10-3 per visit which is equivalent to one collision every 128 vessel visits. This is approximately one order of magnitude higher than the average. A likely reason for this relatively high collision frequency is that for every visit to an installation, the DSV has a much higher “at risk” exposure due to it remaining alongside the installation for a considerable number of hours whereas the other vessel types would remain close to an installation for a much more limited period. It should also be remembered that none of the 21 reported DSV collisions resulted in moderate or severe damage to the installation. The likelihood of a supply vessel colliding with a semi-submersible unit is 1.1x10-3 per visit which is equivalent to one collision every 926 vessel visits. 3.3.6 Collision Frequency Per Vessel Orientation Of the 49 reported collisions of supply vessels with semi-submersible units (Ref. Section 3.3.4) 27 had the orientation of the vessel recorded. A breakdown of the colliding vessel orientation is presented in Figure 3-9. Unknown 45%

Bow 4%

Stern 39%

Sideways 12%

Figure 3-9 Breakdown of Supply Vessel Collision Orientation From Figure 3-9 it can be seen that the majority of collisions, where the orientation of the colliding vessel was known, were stern-on, with sideways collision contributing a large proportion of the remainder. It is impossible, however, to determine the frequency of collision for each of the colliding vessel orientations since there is insufficient historical data on the exposure of each orientation (i.e. the annual number of visits stern-on, sideways, etc.). 3.3.7

Collision Causation Factors - Visiting Vessels

3.3.7.1 Operating Circumstances A distribution of the incidents involving moderate and severe damages is presented in Table 3.11, which gives an illustration of the ratio of collisions involving higher energies. The table gives a breakdown of the incidents according to the operational mode of the vessel when it collided with the installation. Incidents leading to complete failure of the structure have been reported in the period assessed in the J.P.Kenny report. Although the collision incidents reported in the J.P.Kenny work are related to vessels visiting semi-submersibles, the conclusions which can be drawn from the work are considered relevant to all attendant vessel visits to the types of installations considered in this study.

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Table 3.11

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Operating Circumstances Whilst Collision Occurred (Semi-Subs)

Operation

Total No of Reported Incidents

Percentage Contribution

Approach

13

23.6%

9

27.3%

Mooring

8

14.5%

4

12.1%

Cargo Transfer

25

45.5%

14

42.4%

Personnel Transfer

2

3.6%

2

6.1%

Diving Operations

1

1.8%

1

3.0%

Standby Duties

0

0%

0

0

Other/Not Specified

6

10.9%

3

9.1%

55

100%

33

100%

Total 1) 2)

No. of Incidents Resulting in Moderate1) or Severe2) Damage

Percentage Contribution to Moderate/Severe Incidents

Moderate: Incidents involving denting of stiffeners in Semi-Submersibles and incidents where repair was required. Severe: Those incidents where it was possible to calculate the energy absorbed by the struck installation and where the energy was greater than 0.5 MJ.

3.3.7.2 Main Causes of Visiting Vessel Collisions The J.P.Kenny report summarises the following with respect to the causes of visiting vessel collisions: • • • •

Misjudgement and equipment failure were seen to be the primary causes of visiting vessel collisions. Cranes with short reach do not allow supply vessels to stand sufficiently far off the platforms when off-loading, and this could be a contributory cause in some collisions. Fatigue of the vessels crew could have been a contributory cause of some collisions. In many cases marine operations with the supply boat on the windward side of the platform is required, either because the other crane is out of service or the item being brought to the platform is bound for a location that is practical to reach only from the windward side.

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Table 3.12 shows the causes of the collisions between visiting vessels and offshore installations. Table 3.12

Prime Causes of Collision Accidents, Moderate/Severe Damage

Failure Mode

Supply Vessel Approach

Supply Vessel Loading

Standby Vessel Duties

Misjudgement

40 %

34 %

25 %

Equipment Failure

40 %

16 %

50 %

Weather

16 %

24 %

25 %

Mooring Problems

4%

16 %

0%

Other

0%

5%

0%

Not Specified

0%

5%

0%

100 %

100 %

100 %

Total

As the data in the J.P.Kenny report is from 1975-85, one would expect that increasing standards in both the vessels utilised and the marine procedures applied may have resulted in a decrease in the collision frequency (Ref. Section 3.3.8). 3.3.8 Evaluation of Data - Visiting Vessel Collisions For comparative purposes, the results of the assessment presented in Section 3.3.2 to 3.3.6, which are predominantly based on the extensive work performed by J.P.Kenny, were compared with a similar study conducted by Advanced Mechanics and Engineering Ltd. (AME) covering the period 1975 to 1990. The results of the AME study were presented (in part) in a lecture by Charles Ellinas [10]. During the period under consideration AME concluded there was a total of 138 collision incidents on fixed steel platforms. The platform exposure during this period was estimated from the OPL document titled “Subsea Guide and 3rd Edition Field Development Guide” as 908 installation-years. This gives a collision frequency of 0.152 per installation-year. The same reference presented an average risk estimate of 0.028 per installation-year for severe incidents (energy absorbed by the platform exceeding 0.5 MJ). The difference between the estimate of a visiting vessel collision frequency for fixed steel platforms in the UKCS, (based on the J.P.Kenny report) of 0.117 (Ref. Figure 3-4) with that estimated by Ellinas of 0.152 is considered relatively small and would probably be due to random fluctuation in the number of events per year. To compare the frequency of collision for attendant vessels in the UKCS with that of the corresponding sector of the Norwegian North Sea, the results of a report from The Norwegian Petroleum Directorate (NPD) [7] can be used. In the NPD report, a total of 29 attendant vessel collisions were reported on the Norwegian Continental Shelf during the period from 1982 to 1994. Of these, 4 were collisions by shuttle tankers against loading buoys, and the remaining 25 collisions from other vessels, (i.e. attendant vessels of different kinds). With a platform exposure during this period of 880 installation-years, 25 collisions gives a collision frequency of 0.028 per installation-year. This frequency reflects collisions by diving vessels, supply vessels, standby vessels, rescue vessels and pipe laying vessels. 13/06/2003

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The structural damage to the platforms has in general been small or insignificant, with the exception of six collisions causing expensive structural repair work. The reason for the considerable difference between the collisions frequencies found for the UK and Norwegian Sectors (0.117 and 0.028 per annum respectively) is unclear. However, following a review of incident reports carried out by the NPD [7], the reason for the difference in frequency is not due to lack of reporting of Norwegian offshore collisions. Some of the difference may be accounted to different attendant vessel operation procedures, mooring techniques, allowable weather criteria, etc. It should be noted that the statistics from the Norwegian Sector are from the period 19821994 and for the UK Sector 1975-1985 and 1975-1990. The difference in periods, 10 years versus 25 years and the improved incident reporting and operating standards over time could account for the difference. A major development of the supply and standby vessels has taken place from the first generation to the present, modern vessels. Aspects which may be mentioned, are: •

improved man/machine system

•

improved manoeuvring characteristics

•

machinery/electrical back-up systems

•

more reliable components

•

thruster power available

•

introduction of cranes with wider operating ranges

•

the size of the supply vessel's working area

Platform type (jacket, Con-deep, Semi-Sub., etc.), distances to structural elements, alternative working areas related to different wind directions, etc. will also influence the risk of collision. These factors have to be considered case by case. However, no obvious trend in the annual risk estimates for incidents to platforms is seen from AME [10] which presents the annual incident risk for each year over the period considered. It is however worth noting that the NPD collision frequency of 0.028 per installation-year is identical to that presented by Ellinas for collisions with a platform absorbed energy in excess of 0.5 MJ. This indicates that there may be a possible inconsistency in the reporting criteria (e.g. terminology) between the two reporting systems.

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COLLISION FREQUENCY MODELLING

4.1 Introduction This Section gives an overview over which factors which should be considered for collision frequency assessment. The basis for collision risk assessment will be ship traffic data. This could be based on site specific traffic surveys or available traffic databases. 4.2

Ship/Installation Collision Frequency Modelling

4.2.1 Important Factors Affecting Collision Frequency The modelling of collision risk is based on the factors that will influence the collision process, i.e. those factors which will affect the probability of a collision as well as the consequences. Generally, these can be described as : • • •

Location specific factors. Rig/platform specific features. Traffic behaviour.

The collision risk will be more or less proportional to the traffic density. It is therefore important to model the actual traffic pattern(s) in the area studied. The main factors in each of these groups and their influence on the collision frequency are summarised in Table 4.1.

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Table 4.1

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Summary of Factors Affecting Collision Frequency Platform/Rig Location

Characteristics Traffic:

of

Vessel Passing Traffic - Independent of presence of installation varies considerably with location both in terms of number and type of vessels. Dedicated or Attendant Vessels - only present because installation is on that location.

Environmental Conditions: Visibility - fog - snow/driving rain - length of night Wind, current and waves Type of Location

Open water/coastal Few/many platforms in area.

Time at Location

Passing Traffic - affects the probability of being known as well as the proportion of vessels taking precautionary actions. Platform/Rig Features

Type - Fixed or Mobile:

Affects likelihood that ship will know in advance that the platform or rig is at a given location.

Size and design:

Collision frequency is proportional to the effective width/target presented by the platform.

Anchoring System:

Affects number of AHT/supply vessels needed to weigh and lay anchors.

Drilling Activity:

The type of activity being undertaken (e.g. exploration drilling, production drilling, well workover, etc.) will affect both the numbers of supply vessels needed and the duration on location. Logistic For example, size of supply vessel, affecting number of vessels visiting and also potential collision consequences.

Transport Decisions: Collision Measures:

Avoidance Measures taken by installation or its' standby vessel can reduce the risk of collisions. Traffic Behaviour

Vessel's Purpose:

E.g. if it is a visiting vessel it will head for it on a collision course.

Bridge Watch keeping Standards and Reliability:

Will determine probability of errors on the bridge. Varies with type of vessel.

Propulsion/Steering Performance and Reliability:

Affects speed of vessel, and ability to recover to avoid collision. Can be related to size of vessel.

For visiting vessels in particular, references are as well given to the discussion in Section 3.3.7 and 3.3.8.

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4.2.2 Collision Frequency Models According to MaTSU(Marine Technology Support Unit) [11] three models are currently available for predicting the collision frequency of a ship with an offshore platform located in either the North Sea or the Irish Sea. Two are commercially available. The third model is the property of the DGSM (Directorate General of Shipping and Maritime Affairs - the Netherlands). The models have been used extensively within the UK, Norway and the Netherlands to help quantify the risk to an offshore platform from the ship collision hazard. Comparative studies performed for the UK-HSE (OSD) in the UK revealed significant variations in the collision frequencies predicted by the 2 commercial models [11]. 4.3

Vessel Traffic Pattern and Volume

4.3.1 General The traffic volume is probably the parameter which most directly can be based on observations and which can be treated statistically without having to apply analytical considerations or engineering judgement. This is therefore also the parameter which requires the least engineering effort in terms of modelling but will require considerable data gathering effort if the information is not already available. Any database also needs to be updated regularly. Seagoing traffic patterns invariably change with time. To some extent, such changes can be foreseen, but a certain element of unpredictability will always be present. For this reason, it may be wise to perform spot checks whenever a detailed risk analysis is performed or updated. In Section 4.3.2, some factors which are likely to affect the traffic volume have been identified and are discussed briefly. There is no general rule as to how large the influence of each factor will be, this will depend on the platform location and will vary. Nevertheless, these factors may be used as a check list when performing a risk analysis. The discussion gives an indication of influence each factor may have on traffic volume. 4.3.2 Factors Affecting the Traffic Volume The most important factor which will affect the traffic volume are changes in the activity level in the ports which generate traffic into the area in question. In particular for small routes, such changes may have a significant effect on the traffic volume. Many routes in the North Sea have traffic volumes of less than 1000 vessels annually and even if the traffic increases with only one passage per day, the increase in the traffic volume will still be about one third of a route with such a traffic volume. Such changes should therefore be taken into consideration. In most cases, the risk is calculated on an annual basis, and seasonal variations are thus of little importance. However, if one is interested in the risk level during only a limited period, e.g. in order to assess the risk for an installation period or another operation, variations over the year should be assumed.These variations may have several reasons: • • •

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Some routes may be operated during only a part of the year. Typical of these are ferry routes. Due to generally worse weather conditions during the winter there may be differences in choice of route. In some specific cases certain ship traffic may be reduced during parts of the year.

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These aspects should be taken into consideration when the traffic volumes for different routes or areas are estimated. In some cases, such seasonal variations are defined in the routes presented. An effect which is similar to the weather routing effect is the effect of the vessel size. Larger vessels may tend to choose different courses from smaller vessels, either because the water depth is limited or because larger vessels are less affected by bad weather and thus do not have to take such considerations into account. A particular weather related effect is the possibility that routes may be constantly deviated due to prevailing winds and current. This has not been taken into account when the route pattern was established, but may be considered. However, this effect is likely to be marginal because the vessels will correct their courses regularly. If a route passes very close to a platform, the effect may be of some importance because a larger proportion of the vessels than otherwise would be expected may choose to pass the platform on the leeward side. 4.3.3 How to get Traffic Data The three collision frequency models considered by MaTSU in [11] (Ref. Section 4.2.2) have as well integrated traffic databases. Other traffic databases do exist and are also commercially available. A traffic database (traffic volume, traffic pattern, ship sizes, ship speeds, etc.) could be established for a certain project based on the following sources (this could be necessary if traffic databases for the specific area are considered not to be of adequate quality, not updated or not existing): • • • • •

Data from Lloyds Maritime Information Services (or similar) to determine the number of merchant vessel movements as well as the types and sizes. Information on the movements of ferries, shuttle tankers and offshore vessels (supply and standby vessels) as provided by ferry and offshore operators respectively. Traffic surveys carried out by standby vessels, dedicated survey vessels and platform and shore based radar systems, to determine the positions of the different routes as they pass through survey locations. Information provided by the Coastguard, the defence and/or harbour authorities. Information provided by mariners and vessel passage plans

Several data sources should be combined in order to determine the route patterns.

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COLLISION CONSEQUENCES

5.1 General This datasheet puts emphasis on the determination of the likelihood of various types of collision for a range of vessel and installation combinations. The consequences in the event of a collision are not covered in detail here. Consequence analysis would be on a case specific basis and take into account: • • • • •

Installation type: 1) Fixed: steel, concrete, tension leg etc, 2) Jack-up, 3) Semisubmersible Impact duration compared with the natural period of the installation motion Mass, velocity, impact direction and energy absorbtion characteristics of the colliding vessel and impacted installation Structural response of the vessel and installation Potential escalation events following initial impact (eg loss of containment, fire, explosion, evacuation, escape and rescue) covered in other datasheets.

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RISK REDUCING MEASURES

Risk reducing measures and their effect has been considered in many research projects, among them [12] and an ongoing UK HSE project (Ref. Section 7.3). 6.1

Use of Risk Reducing Measures

Risk reducing measures comprise probability reducing as well as consequence reducing measures, including contingency measures. Priority should be given to risk reducing measures which can detect the potential for collision as early as possible and which can contribute to avoiding the collision. (For example, a warning of a potential collision as early as possible via a collision warning system on the platform and/or standby.) This is often also the most effective way to reduce the collision risk. Reducing the consequences of a collision, primarily by increasing the impact resistance of the platform will, in many cases, require significant effort and investment to be effective. 6.2

Overview of Risk Reducing Measures

The effect of different risk reducing measures can most readily be identified by looking at the modelling which has been used for the different vessel groups. • • • •

Powered passing Drifting passing and drifting nearby Powered nearby Floating Unit in Drift

A systematic approach to identification of risk reducing measures will be to look at the different parameters modelled and see whether it is possible to affect the parameters to reduce the risk.

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RESEARCH AND DEVELOPMENT PROJECTS

7.1

Introduction

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Currently there are three known ongoing research and development projects related to collision risk in the North Sea.

7.2 UK Continental Shelf Shipping Traffic Database A joint industry project started early 1995 to create a database of shipping patterns on the UK Continental Shelf (UKCS). It is sponsored by the UK Department of Transport, UK Offshore Operators Association (UKOOA) and the UK Health and Safety Executive (HSE). Vessel traffic data is being collected by standby vessels, platform and onshore based radar systems throughout the UKCS, supported by information from Lloyds’ port logs of vessel movements across Europe. The first and main phase of the project, which was to establish a traffic database, was completed in January 1996 [13]. There were several objectives for establishing the database. First of all it is desirable to know where the major shipping routes are concentrated around UK waters allowing for assessments of environmental risks associated with shipping. This way the determination of the best locations for rescue, salvage and counter pollution resources around the UK can be done. Another objective is to establish the location of major shipping routes in relation to future oil and gas developments. The HSE wishes to establish a reliable database that can be used to predict the risks associated with collisions between passing vessels and offshore installations. This will provide some standardisation to the industry and encourage operators to obtain an understanding of the traffic patterns around their offshore installations and use this to evaluate risk and develop emergency plans and resources to manage the risk. The database which is commercially available, will be updated annually to ensure that it remains reliable and up to date. The work planned for next phase includes establishment of chart plots, further traffic surveys to be carried out and analysed, and collections of further information on offshore field related traffic. 7.3

The Effectiveness of Collision Control & Avoidance Systems

This project is carried out for the HSE. Several topics are considered. The first task is identification and review of systems currently utilised by duty holders on the UKCS to identify and control the threat posed by shipping, and identification of any other systems in use world-wide or other transport sectors where a collision threat exists. The prime accident causation factors in collision scenarios are determined, and it is identified how a general collision avoidance system may intervene. A qualitative review of the effectiveness of these systems upon the causation factors is done, followed by a quantification of the effectiveness. Finally an evaluation of the systems identified is performed, to see how they could improve or complement any of the systems currently in use.

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7.4

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Comparison of ship-platform collision frequency models.

The background for this study is that regulatory bodies covering the different international sectors of the North Sea would like to develop a standardised risk assessment method to guarantee consistency in the safety management. This is based on the fact that ship collision risk is one of the major external factors contributing to the risk to an offshore installation, and that a critical review of the existing collision models has revealed large differences between the models. The project, which is sponsored by several authorities around the North Sea.

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REFERENCES

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9 1)

Dovre Safetec AS; SAFETOW Reference Manual - Risk Assessment of Towing Operations, Draft Report No. ST-95-CR-015-00, December 1995.

2)

J. P. Kenny; Protection of Offshore Installations Against Impact, Report No. OTI 88535, 1988.

3)

NPD: Regulation of Structural Design of Loadbearing Structures..., 29. Oct. 1984

4)

Department of Energy, Offshore Installations, Guidance on design, Construction and Certification, Fourth Edition, January 1990

5)

Health and Safety Executive, Update of UKCS Risk Overview, Offshore Technology Report, Report No. OTH 94 458.

6)

Det Norske Veritas, World Offshore Accident Data base.

7)

The Norwegian Petroleum Directorate, Båtkollisjoner - Fase 1, OD-94-50

8)

Marine Technology Directorate Ltd, Guide to Offshore QRA Collision Risk - draft, July 1995

9)

Technica Ltd., Risk Assessment of Buoyancy loss, Ship-MODU Collision Frequency, Report No. 3, July 1987

10 )

Charles Ellinas (Advanced Mechanics & Engineering Ltd), Ship/Installation Collision Data, International Workshop on Data for Oil & Gas QRAS, E&P Forum - London 15.12.93.

11)

MaTSU(Marine Technology Support Unit); A Critical Review of Ship-Platform Collision Frequency Models; MaTR/1020, 19.06.95.

12)

Dovre Safetec AS (earlier SikteC), Collide II - Reference Manual, Report No. ST-91-RF-032-01, November 1991

13 )

Dovre Safetec Ltd, UKCS Vessel Traffic Database - Project Report, Report No. DST-95-CR-110-01, January 1996

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EXTREME WEATHER RISK

21/03/97

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Extreme Weather Risk

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SUMMARY Extreme Weather Risk for Fixed Units For fixed steel platforms the extreme weather risk may be estimated using a validated reliability model. results using this model are summarized in Table A for the Gulf of Mexico and for the North Sea areas, for both existing and new structures. These results are based on generic assumptions about each sub-population with respect to the design basis and the resulting strength. The values in Table A may be used in lieu of more detailed studies for the specific installation, but it should be recognized that they are necessarily approximate and generally would tend to overpredict the failure rate. Where installation specific data is available the estimate of the probability of failure may be further improved as discussed in Section 2.5 of this Note. Table A: Calculated failure rate per annum:

Geographical Area Gulf of Mexico North Sea

Installation Pd. pre- 1971 0.02