CR FPP 170 H2S Policy Rev 02
Short Description
spe...
Description
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 2 of 28
Table of Contents 1. RECAP OF RULES ............................................................................................... 5 2. FOREWORD ......................................................................................................... 7 2.1
Indicator......................................................................................................................... 7
2.2
Glossary ........................................................................................................................ 7
2.3
Introduction................................................................................................................... 8
3. H2S CHARACTERISTICS ..................................................................................... 8 4. SAFETY PLANNING ........................................................................................... 10 4.1
H2S toxicity.................................................................................................................. 10
4.2
H2S occurrence ........................................................................................................... 12
5. CONTROLLED DRILLING ENVIRONMENT (CDE)............................................ 13 5.1
Definition ..................................................................................................................... 13
5.2
CDE achievement ....................................................................................................... 13
5.3
Limitation..................................................................................................................... 16
6. REQUIREMENTS FOR OPERATIONS............................................................... 17 6.1
Requirements for drilling or WO operations........................................................... 17
6.2
Requirement for a light intervention......................................................................... 25
6.3
Ignition of a blow out containing H2S ....................................................................... 26
7. REQUIREMENTS FOR MATERIAL.................................................................... 27 7.1
Casing/Tubing Material .............................................................................................. 27
7.2
Wellhead, Xmas Tree, MLS and Downhole Equipment .......................................... 27
7.3
Drill Through Equipment............................................................................................ 27
7.4
Drill String ................................................................................................................... 28
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 3 of 28
Reference documents Unless otherwise stipulated, the applicable version of the reference documents listed below, including relevant appendices and supplements, is the latest revision published. Standards Reference
Title
NACE MR 01 75 Rev.03
“SSC resistant metallic materials for oil field equipment
API RP 49 – 2nd edition
RP for safe drilling of wells containing H2S
API RP 13 B1 & B2
Field testing for drilling fluids
API SPEC 6A–16 th edition Specifications for WH & Xmastree equipment API SPEC 16A–1st edition
Specifications for drill through equipment
Professional Documents Reference
Title
DFP Manual
Blowout Contingency Plan – chapter F
EMF 93 #1
Manual “Selection of materials for well equipment”
Regulations Reference
Title
Not applicable
Codes Reference
Title
Not applicable
Other documents Reference
Title
Not applicable
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 4 of 28
Other Total documents Reference
Title
CR FPS 110
Bridging document
CR FPP 150
Casing and Tubing
CR FPP 225
Casing Design
CR FPP 310
Tubing calculation
GS COR 170
Material for sour service – Specification for design
CR FPP 245
surface wellhead, surface X-mas tree and MLS
CR FPP 246
subsea wellhead and X-mas tree
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 5 of 28
1. RECAP OF RULES Rule 1:
Each operation programmed under the FP’s responsibility must be classified according to H2S occurrence levels. For drilling, each phase shall be considered separately.
Rule 2:
H2S occurrence level must be systematically reassessed according to drilling, mud logging and electrical logging data collected prior to formation testing.
Rule 3:
CDE in water based mud means the 3 following actions are conducted simultaneously: y PH of mud maintained above 11 y Global sulfides in mud and filtrate monitored y Soluble sulfides in mud eliminated using scavengers Monitoring of sulfide content is made by: y Lead acetate paper (Qualitative) y G.G.T. (Quantitative)
Rule 4:
CDE is a normal objective and of normal practice when H2S is foreseen. When H2S occurrence is level 1 or 2, sour service material for casing and well control equipment must be selected.
Rule 5:
Should H2S be encountered above the foreseen occurrence level with consequently no more valid H2S procedures, operation progress must stop immediately.
Rule 6:
For H2S occurrence level #2, an ‘’H2S and safety/protection equipment’’ dedicated training shall be systematically delivered to all personals coming on the rig site.
Rule 7:
Independently of H2S occurrence level, an oxygen resuscitator kit shall be kept permanently operational on the rig (sickbay). For H2S occurrence level #2, an oxygen resuscitator kit shall be made available on each dedicated stand-by boat during all H2S operations.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rule 8:
Rev: 02
Date: 19/05//2004
Page: 6 of 28
In case of H2S occurrence #2, all specific H2S procedures should be detailed in
a dedicated contingency plan, jointly approved by drilling and safety departments, the drilling contractors and, if applicable, the production department and H2S company. Rule 9:
As soon as the ‘’sour environment’’ criteria can be foreseen, typically H2S occurrence level 1 (possible) and level 2, all parts of the first confining barrier (casing, wellhead and BOP) must be ‘’sour service’’.
Rule 10: For each well with the potential for Hydrogen Sulfide (H2S), the ignition or not of a blow out containing H2S shall be stated in the BOCP and in the well programme based on the local conditions and H2S/SO2 dispersion studies.
Rule 11: If an H2S trim BOP is required, it is imperative to verify that the installed shear/blind blades are H2S proof. Rule 12: Drill strings shall never be used for acidification or drill stem tests (DSTs) on wells where H2S risk is identified (H2S occurrence #2).
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 7 of 28
2. FOREWORD
2.1 Indicator Rule which needs derogation Main recommendation or useful information
2.2 Glossary BHA
Bottom hole assembly
BOCP
Blow Out Contingency Plan
BOP
Blowout preventer
CDE
Controlled Drilling Environment
CT
Coil Tubing
DST
Drill stem test
HIC
Hydrogen Induced Cracking
HRC
Hardness Rockwell
GGT
Garret Gas Train
GOR
Gas/Oil ratio
LCM
Lost circulating material
MLS
Mud Line Suspension
NDE
Non Destructive Examination
OBM
Oil Base Mud
PH
Alkalinity
Pm
Total alkalinity of the mud including hydroxides, carbonates and bicarbonates
SABA
Supplied Air Breathing Apparatus (10 minutes autonomy)
SCBA
Self-Contained Breathing Apparatus (45 minutes autonomy)
SSC
Sulfide Stress Cracking
WBM
Water Base Mud
WO
Work-Over
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 8 of 28
2.3 Introduction Hydrogen Sulfide is one of the critical problems that can be encountered while drilling or performing well interventions. The presence of this gas will affect: y Personnel due to the extreme toxicity of this gas, y Equipment because of sulfide stress cracking phenomena affecting most high strength steels. The document takes into account the official recommendations issued by: y The American Petroleum Institute (API RP 49, 2nd Edition, April 15, 1987) : "Recommended Practices for safe drilling of wells containing Hydrogen Sulfide". y The National Association of Corrosion Engineers (NACE Standard MR-01-75, 1993 Revision): "Sulfide Stress Cracking Resistant Metallic Materials for Oil Field Equipment". Note : Reference is not made to the “ISO 15156” standard, this document being not finalized at this time. It must be kept in mind that “sour service” criteria mentioned in this future standard will slightly differ from current NACE requirements.
3. H2S CHARACTERISTICS Naturally occurring H2S has two main origins: a bacterial origin and a chemical one. y Bacterial origin is linked to areas that are considered petroliferous and contain evaporite beds (anhydrite, gypsum). y Chemical origin (degradation of organic sulfur) is linked to carbonate source beds favorable for such a reaction. This explains why most of the gas deposits containing high H2S percentages are in carbonate reservoirs (Lacq with 15% H2S or Devonian deposit in Alberta with 88% H2S). However, H2S can also be the result of some operations performed during drilling, testing or completion of a well such as: y Decay of lignosulfonates or other fluid additives into sulfides, which can lead to H2S generation y Introduction of sulfate reducing bacteria in drilling fluids that can cause H2S generation in non active mud pits (LCM pills or kill mud pits) or in reservoirs susceptible to extensive losses y Acid attack of insoluble sulfides, present in the formation or formed by most H2S scavengers with H2S, during an acid job
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 9 of 28
For various reasons (poor treatment, reaction with pyrites, etc), water injection for secondary recovery may also generate H2S. Volume of H2S generated during these operations is generally limited. Nevertheless the danger remains and all personnel must be aware of these potential origins. It is always of benefit to understand the source of the H2S in the event of an H2S alarm. The main physical properties of H2S are: y Colorless gas, extremely poisonous, strong nauseating odor in weak concentrations y Heavier than air: specific gravity (gas @ 15° C, 1 atm) = 1.19 (1 for air) y Explosive at concentrations between 4.3% and 45% (5% Æ 15% for Methane) y Spontaneous combustion occurs at 260°C (500°F), compared to 537°C (1000°F) for Methane y Burns with a blue flame and produces Sulfur dioxide (SO2), which is also toxic but much less y Soluble in water and very soluble in oil y Make some steels brittle under certain temperature conditions y Contaminates water based drilling mud: main effects are a drop in pH level, a strong amplification of rheological properties and a visual darkening of mud y H2S density = 1.54 g/l. Notes: 1) 1 ppm H2S is equivalent to 1.54 mg H2S / m3 or 1*10-4 % H2S or 1 % H2S is equivalent to 15.4 g H2S / m3 or 10000 ppm H2S 2) The H2S partial pressure is equal to the mole fraction of H2S in gas phase multiplied by the global system pressure: For example: If the concentration of H2S in gas phase = 100 ppm and if the Global pressure = 3000 psi, then H2S partial pressure Æ 100* 10-6 * 3000 = 0.3 psi
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 10 of 28
4. SAFETY PLANNING
4.1 H2S toxicity The extreme toxicity of H2S for human life is reminded in the next table. The main points to remember are: y Very unpleasant odor at very low concentration but this gas affects rapidly the sense of smell y 10 ppm in air is the maximum concentration for continuous work on a tour period (but local legislation may be more severe); exposure levels exceeding this value require use of personnel protective breathing equipment y 50 ppm is the ceiling limit for short exposure periods: eyes irritation appears quickly y H2S poisoning by successive short exposures is not cumulative Reminder:
Anybody, which has accidentally inhaled air with high H2S concentration, must be immediately brought in the breathing area and artificially ventilated.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 11 of 28
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 12 of 28
4.2 H2S occurrence As soon as an operation is programmed (drilling/completion, W.O. or light intervention), risks of encountering H2S during operations must be systematically assessed and clearly recorded in the common geological & drilling well program or other intervention technical program. Three levels of risks can be typically foreseen: y H2S occurrence #0: No H2S risks; the geological basin is well known and no H2S has never been recorded. y H2S occurrence #1: H2S risk is reduced but cannot be totally ignored: Æ Presence of natural sulfides which can be transformed by acid Æ Operations on appraisal or development wells crossing water levels which may contain some shows of H2S Æ Drilling of exploration wells in areas theoretically free of H2S but bottom pressure is greater than 5000 psi y H2S occurrence #2: Unquestionable risks of H2S: Æ All operations on exploration wells in areas known as potential H2S bearing Æ All operations on delineation or development wells through formations known to be H2S bearing Æ W.O. or interventions on wells in communication with reservoirs containing H2S Æ Formation Testing on layers where H2S has been identified during drilling operations. Rule 1:
Each operation programmed under the FP’s responsibility must be classified according to H2S occurrence levels. For drilling, each phase shall be considered separately.
Rule 2:
H2S occurrence level must be systematically reassessed according to drilling, mud logging and electrical logging data collected prior to formation testing.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 13 of 28
5. CONTROLLED DRILLING ENVIRONMENT (CDE)
5.1 Definition A Controlled Drilling Environment (CDE) means that, even if some reservoirs containing H2S are drilled through: y No gaseous H2S can appear at surface y No atomic hydrogen is formed at any depth within the well For that, H2S must be neutralized as soon as it can enter the well. The role of drilling fluid is of course essential.
5.2 CDE achievement
5.2.1 In WBM (Water Base Mud) : y The first step in achieving a CDE is to maintain the pH (Alkalinity) of the mud high enough (10-11) to allow H2S dissociation while minimizing the presence of atomic hydrogen at the source of SSC. In such environment soluble sulfides are produced if H2S is present. But if mud pH drops for any reason, these sulfides can recombine immediately to form gaseous H2S that can lead to a dangerous situation. Sufficient alkalinity provision in the mud should avoid this risk (Pm > 3). y The second step in achieving a CDE is then to eliminate the soluble sulfides in mud using sulfides scavengers. Numerous scavengers exist for WBM; the most popular is the “ironite sponge” (iron oxides) but zinc based scavengers are also available. Whatever the type of scavenger used, insoluble metal sulfides are formed. The constraint is that gaseous H2S will be produced from metal sulfides in case of acidification; consequently acid spots is not recommended if drill string is stuck.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Page: 14 of 28
Date: 19/05//2004
The list of common chemicals used as scavenger is given below: Trade Name
Type
Company
MILGARD
H2S extractor - Basic zinc carbonate
BAKER
MILGARD L
Liquid zinc chelate
BAKER
IRONITE SPONGE
Solide H2S scavenger
IRONITE
SAFE SCAF HS
Soluble H2S scavenger
M.I.
SS10
H2S remover
OSCA
SOURSCAV
H2S remover
BAROID
ZINC CARBONATE ZINC OXYDE
All companies Zinc source for OBM -H2S removal
All companies
The following figures give respectively: y The repartition of different sulfides function of the medium pH (Figure 1) Fig. 1
DANGER
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Page: 15 of 28
Date: 19/05//2004
y Possible H2S concentration in air above mud function of total sulfides in mud (Figure 2)
H2S (ppm) in air 1.000
Fig. 2
pH = 8
Collapse unconsciousness death
pH = 9 Loss of sense of smell 100
pH = 10
pH = 11
Maximum safe working level
10
pH = 12
Global sulfides dissolved in mud
1
10
Rule 3:
100
1.000
CDE in water based mud means the 3 following actions are conducted simultaneously: y pH of mud maintained above 11 y Global sulfides in mud and filtrate monitored y Soluble sulfides in mud eliminated using scavengers Monitoring of sulfide content is made by: y Lead acetate paper (Qualitative) y G.G.T. (Quantitative)
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 16 of 28
5.2.2 In OBM (Oil base mud) : With OBM, risks of SSC are minimized as the oil phase coats and protects metal surfaces; but on a other hand, H2S is highly soluble in oil and sulfide detection in such a mud is a little more difficult; in addition scavengers efficiency is reduced. Mud characteristics are affected by H2S influx (Emulsion stability, HP/HT filtrate, and rheology). Free lime is often used in OBM to neutralize H2S influx. ZnO can also be added as complementary scavenger; but H2S influxes not totally neutralized when entering the well will dissolve in OBM and liberate gaseous H2S on surface. More attention should therefore be paid to surface detection system and crew reactivity. Then if possible, OBM should be avoided if H2S bearing levels are foreseen.
5.3 Limitation To keep the return fluid pH at the right value may be questionable during a kick and even in CDE, free H2S may appear. SSC can therefore be a concern and sour service material must be selected for the structural well barrier. Regarding drill string, risks of failure exist but workload can eventually be monitored and first of all, consequences shall be more limited. Therefore only specific drilling cases (shallow acid gas wells with high risks of kick, abnormal string breaks, etc) can justify sour service drill pipes. Rule 4:
CDE is a normal objective and of normal practice when H2S is foreseen. When H2S occurrence is level 1 or 2, sour service material for casing and well control equipment must be selected.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 17 of 28
6. REQUIREMENTS FOR OPERATIONS
6.1 Requirements for drilling or WO operations Equipment and procedures must be adapted to each previous H2S occurrence levels. Requirements apply to the following parts: y y y y
Safety Tubular, wellhead and well control equipment material CDE Rig equipment
The first point should be integrated to the contingency plan relating to the foreseen operations. Rule 5:
Should H2S be encountered above the foreseen occurrence level with consequently no more valid H2S procedures, operation progress must stop immediately.
The well must be either temporarily secured so as to allow compliance with dedicated requirements, or definitely plugged and abandoned, should the former option be impossible. Cost cannot be taken into consideration for such a decision.
6.1.1 Safety Rule 6:
For H2S occurrence level #2, an ‘’H2S and safety/protection equipment’’ dedicated training shall be systematically delivered to all personnel coming on the rig site.
Rule 7:
Independently of H2S occurrence level, an oxygen resuscitator kit shall be kept permanently operational on the rig (sickbay). For H2S occurrence level #2, an oxygen resuscitator kit shall be made available on each dedicated stand-by boat during all H2S operations.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 18 of 28
6.1.1.1 In case of H2S occurrence #0 Detection:
One fixed H2S alarm system with alarm set at 5 ppm in air; alarm should raise in the drill floor area, mud logging cabin (if installed) and tool pusher’s office. Electronic sensors are installed : y y y y
On mud logging unit degasser (if installed) On flow line On return mud pit On rig floor
Reminder: H2S detectors must be carefully protected against water projection, regularly calibrated and tested to be sure they are fully operational. One electronic portable detector shall be permanently available at hand in the drill master cabin and in living quarters. Protection:
No protective equipment is required. However and firstly if reservoirs coring and/or sampling are foreseen, a minimum set of escape masks equipped with H2S filtration cartridge and/or SABA should be available on the rig floor. Reminder: Protective equipment must be checked and crew be trained on the use of masks before the critical foreseen operation. Communication:
No specific transmission system in addition of basic rig intercom system. Procedures:
No specific procedures excepted general instructions in case of H2S alarm.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 19 of 28
6.1.1.2 In case of H2S occurrence #1 Detection:
One complete H2S alarm system with alarm set at 5 ppm in air; alarm should raise in the drill floor area, shale shakers, mud logging cabin, mud pits / pump area and tool pusher’s office. Electronic sensors are installed: y y y y y
On mud logging unit degasser On flow line On return mud pit On rig floor One independent alarm at air intakes of living quarters
Portable detectors available in dog house, mud room and living quarters. Protection:
Escape masks with H2S filtration cartridge and/or SABA available in dog house, mud room and mud logging cabin (in sufficient number for working shift personnel). 4 self-contained breathing apparatus of medium capacity (45 minutes) available in offices or living quarters (with adequate air refilling system). Communication:
An efficient intercom system should exist between all strategic/work points of the rig. A phone link should be operational onshore between camp and rig. Procedures:
Procedures and responsibilities in the event of an H2S alarm must be clearly defined and joined to the operation program. Specific procedures and special care when opening a sampler or when recovering a core at surface. Rig evacuation drills without change. Periodic briefing on perfect maintenance and use of escape masks and portable breathing systems. Normal and emergency communication systems on rig and between rig and stand by boat must periodically be tested. This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 20 of 28
6.1.1.3 In case of H2S occurrence #2 All specific equipment needed must be kept in perfect working conditions and regularly tested. It is highly recommended to hire this equipment from a H2S Services Company along with the services of an H2S Supervisor. The latter will take care of onsite continuous people training and awareness, equipment maintenance, air refilling operations, H2S and SO2 monitoring. Of course material and crew should be fully operational prior H2S problems can be encountered. Detection:
Two independent fixed H2S alarm systems (from mud logging company, drilling rig contractor or H2S services company,) with alarm set down at 10 ppm in air. Alarm should raise in the drill floor area, shale shakers, mud logging cabin, mud pits / pump area and tool pusher’s office. Electronic sensors are installed: y y y y y y y
On mud logging degasser On flow line On shale shakers On return mud pit On cellar deck On rig floor On any critical place where H2S, heavier than air, can accumulate (will depend on rig configuration and ventilation).
An independent H2S detection system shall be installed offshore at air intakes of living quarters (may be considered onshore at the rig camp). Dedicated portable H2S detectors given to tool pusher, mud engineer, mud logger, company man, barge master, supply captains. Two portable tubes gas detector pumps with H2S and SO2 detector tubes. Lead acetate paper. For well testing with H2S, the detection system needs to be adapted to the well testing set up. In particular, SO2 detection should be installed at the well test area and at air intakes of living quarters.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 21 of 28
Protection:
Two breathing areas are prepared onshore, each sides of rig, prevailing winds considered. Offshore, one breathing area/muster point will be prepared; helideck shall often remain the best muster point if H2S is a concern. All personnel equipped with one dedicated SABA; at least 50 % POB spare SABA available on rig (dispatched at main critical areas). As soon as an H2S formation level can be met, this mask must be wear at all time when on rig location (onshore) or outside of the living quarters (offshore). A minimum set of SCBA of medium capacity (45 minutes) should be available on rig: typically 12 on an offshore rig, 6 on a land rig. Cascade breathing air system for a long-term work in H2S environment : each work place should be equipped with air plugs manifold (including cranes). It is also recommended to equip the muster point and the life boats platforms with plugs manifolds on small drilling unit (jackup, compact rig). Air compressors (2 minimum) shall be located at the breathing area. This complete system (compressors, accumulators, regulators and plugs manifold) shall be designed according to operations and evacuation plan. An assessment on lifeboats capacity, taking into account the expected air breathing system embarked, has to be done. Supply vessels need SCBA capacity for the deck crew so as to be able to disconnect mooring lines and move up wind in case of an H2S alarm on the rig. Communication:
In addition of an efficient rig intercom system (and camp/rig phone link onshore) a public address system connected on backup power supply shall be installed. Chalkboards or notepads shall be available to assist communication. Appropriate caution signs and flags shall be placed onshore at all possible location entrances. Additional wind direction devices should be visible from any work and breathing areas.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 22 of 28
Procedures:
Rule 8:
In case of H2S occurrence #2, all specific H2S procedures should be detailed in
a dedicated contingency plan, jointly approved by drilling and safety departments, the drilling contractors and, if applicable, the production department and H2S company.
Drilling or W.O. programs should systematically remind and refer to relating points in applicable H2S contingency plan. Two classifications must be done prior to set up an H2S contingency plan: y An H2S rig areas classification, typically: Æ “H2S 0” area: areas where H2S should not be encountered (due to wind, relative height or pressurization) ; should of course be periodically checked. Æ “H2S 1” area: areas normally safe but should be systematically checked ; escape masks has to be carried. Æ “H2S 2” area: areas with potential danger once H2S alarm has been activated; in that case their access should only be permitted to dedicated personnel, equipped with SCBA and never alone. y An H2S operating conditions classification, typically: Æ NO ALERT LEVEL if H2S is not detected in the atmosphere, sulfides may have been detected in mud and/or H2S may have been detected in extracted gas. Æ ALERT LEVEL 1 if H2S concentration in the atmosphere is below or equal to 10 ppm somewhere on the rig. Æ ALERT LEVEL 2 if H2S concentration in the atmosphere is exceeding 10 ppm somewhere on the rig. H2S contingency plan content: In addition of previous classifications, an H2S contingency plan will include at least: y The list and assignment of essential personnel (people which stay on board in the event of a partial evacuation) y The specific H2S training y The organization and periodicity of safety drills y The responsibilities and duties of individual according to operating conditions classification y The breathing apparatus policy y The rig evacuation policy y H2S specific procedures for normal conditions (alert level 0) : tripping, coring, kick control, WL operations, sampling, well testing y The emergency procedures Æ alert level 1 y The emergency procedures Æ alert level 2 This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
y y y y y
Rev: 02
Date: 19/05//2004
Page: 23 of 28
The environmental limitations versus operations Stand-by vessels communication and safety procedures Neighboring rigs or platforms communication and safety procedures The platform evacuation procedures The local population communication and evacuation plan (onshore).
6.1.2 Casings/Tubings, Wellhead and Xmastree H2S occurrence #0 : Standard equipment can be chosen. If H2S is detected and sour environment possible, operation must be stopped immediately and well plugged. Operations will resume only if H2S service equipment can be installed and any inadequate casing part be covered by a suitable string. H2S occurrences #1 or #2: The first confining envelop must be sour service within the expected operational conditions. Rule 9:
As soon as the ‘’sour environment’’ criteria can be foreseen, typically H2S occurrence level 1 (possible) and level 2, all parts of the first confining barrier (casing, wellhead and BOP) must be ‘’sour service’’.
6.1.3 Controlled Drilling Environment (CDE) y H2S occurrence #0: No specific requirement y H2S occurrence #1: Sulfides detector (GGT or mud duck) will be operational on site and mud engineer aware of its maintenance and procedures. In case of water base mud, a minimum corrosion inhibitor storage will be available on site as well as the required Na(OH)2 to rise the PH of the mud if necessary. y H2S occurrence #2: Probable occurrence of H2S will affect the mud program and specific mud engineer training. Sulfides detection will stay active during all the critical phases and sulfides inhibition process ready to be put on stream; enough scavenger storage should be kept on site. Monitoring of global sulfides in mud and filtrate will be clearly recorded. Mention that, in case of BHA stuck, acidic slug must be prohibited.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 24 of 28
6.1.4 Drilling/WO Rig In any case and independently of the considered H2S occurrence level: y Rig components should be arranged on location (onshore) or rig correctly oriented (offshore) to take advantage of prevailing winds and keep living quarters, camp, engines and helideck upwind from any source of vented gas; a windsock is installed and correctly lighted, easily visible from the driller’s position and helideck. y Escape ways must be properly indicated, lighted and kept free from obstruction. y Gas exhaust from atmospheric degasser is lined to crown block; a direct overboard line stays present. The Specific requirements are: y H2S occurrence #0: No specific requirement y H2S occurrence #1: Æ Well control equipment must be H2S service and BOP arrangement conform to specifications given in CR FPP 160 . Æ Operational mud logging equipment and staff y H2S occurrence #2: In addition of occurrence #1 requirements, the following arrangement is strongly recommended: Æ Cascade air breathing system with accumulators and plugs manifolds rightly sized Æ The derrick vertical exhausts from atmospheric and vacuum degassers shall be diverted on request to horizontal lines; this diversion must be clearly indicated. Æ Offshore flarebooms (floating rigs, jackups) will be permanently deployed on both side of the rig (excepted DP rigs) fitted with a positive ignition source. Diverted lines from poor boy and vacuum degasser are directed to the flarebooms. Depending on the vessel installation and prevailing winds only one boom may be sufficient on a jacket assisted by a tender vessel. Should flarebooms not be available, specific horizontal exhaust lines shall be fixed. Æ Large explosion proof blowers or fans should be installed as a protection against low wind (drill floor, shale shakers) or any open location badly ventilated where H2S may accumulate. Æ Inside ventilation system should be correctly designed; differential of pressures between rooms must be periodically measured (idem OBM drilling requirement). Air system in accommodation quarters shall be on a closed internal circuit with possibility to close external air intakes and vents. Æ Onshore camp should be installed at 1000m minimum upwind from rig.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 25 of 28
6.2 Requirement for a light intervention In case of a light intervention classified “H2S occurrence #2” with or without any drilling or W.O. rig on site, intervention program should clearly mention: y The logistical and safety means insuring adequate work in H2S environment, safe breathing area and possibilities for a prompt escape if any. y The verification of H2S suitability of all equipment (directly used and back-up). y The working limitations that all foreseen equipment (coil tubing, Wire line) can have in H2S environment (rating, working cycles number). y The user’s procedures to limit SSC occurrence and consequences (inhibitor use, high pH fluid injection). y This needs the presence of an H2S supervisor in charge of the training of all personnel (technical and supporting), arrangement and maintenance of all detection, protection and communication equipment. Relating program should be jointly approved by: Æ Drilling/Completion department, Æ Production department, Æ Contractor in charge of the operation, Æ H2S company if any.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 26 of 28
6.3 Ignition of a blow out containing H2S Rule 10: For each well with the potential for Hydrogen Sulfide (H2S), the ignition or not of a blow out containing H2S shall be stated in the BOCP and in the well programme based on the local conditions and H2S/SO2 dispersion studies. The recommended method to ignite a blow out is with a flare gun used from a safe area on the upwind side. Several flare guns with spare flares should be available on site, with adequate SCBAs for the ignition team. Flares that fit in a shot gun will give more range. Specific training/drills to use the flare gun should be done on site at a regular basis. However a back up solution should exist adapted to the specific case.
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 27 of 28
7. REQUIREMENTS FOR MATERIAL
7.1 Casing/Tubing Material Refer to CR FPP150: casing and tubing chapter 4. Nota : Material selection is defined with respect to severity regions from 0 to 3, defined by reference to ISO 15156. These severity regions are defined versus two corrosion related parameters : the H2S partial pressure and the pH. It must be considered that there is no formal equivalence between the H2S occurrence # 0 to 3 (related to human Heath and Safety criteria) and the severity regions from 0 to 3 (related to corrosion criteria), although both are linked to the H2S concentration.
7.2 Wellhead, Xmas Tree, MLS and Downhole Equipment Refer to CR FPP245: surface wellhead, surface X-mas tree and MLS and CR FPP 246: subsea wellhead and X-mas tree.
7.3 Drill Through Equipment Further information is provided in CR FPP 160 ‘’Well Control Equipment’’. Specifications for Drill Through Equipment are covered by API SPEC 16A which states the following: "With the exception of shear blades, all metallic materials which come in contact with the well fluid shall meet the requirement of NACE Standard MR-01-75 for sour service." Formely shear blades were made of high strength steels, which were not always manufactured to be compatible with H2S. But nowadays special super trim shear/blind rams are currently in use. Rule 11: If an H2S trim BOP is required, it is imperative to verify that the installed shear/blind blades are H2S proof. With regard to marine drilling risers, CDE may be effective on the main tubular as any kick will be evacuated through the choke line. In addition this riser does not justify high strength steel excepted on specific component (ball joint). Kill and choke lines shall be specified as ‘’H2S service’’. This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
Company Rule
CR FPP 170 H2S Policy
Exploration & Production
Rev: 02
Date: 19/05//2004
Page: 28 of 28
7.4 Drill String Generally drill string components are for use in controlled drilling environment and therefore conventional API SPEC 5D grades (E, X95, G105 and S135) may be used even if not SSC resistant. Non-API SSC resistant drill pipes with grades up to 110Ksi are available for specific applications if foreseen problems justify their use (unbalanced works, probability of H2S kicks, etc.). It should be verified in addition that relevant tool joints are not susceptible to H2S. Real mechanical properties of these pipes must be assessed. The following can improve the work with standard drill strings in a CDE: y Use of correct make-up torques to avoid excessive stress, y Use of corrosion inhibitors, y Increase in the frequency of BHAs inspections.
If an “H2S service” drill string is required, all crossovers and specific joints inserted in string up to surface should be compatible with H2S. As previously stated, due to reduced yield strengths, this can result in lower capacities than standard equipment. Rule 12: Drill strings shall never be used for acidification or drill stem tests (DSTs) on wells where H2S risk is identified (H2S occurrence #2).
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
CR FPP 170 H2S policy rev 02.doc
View more...
Comments
