12 Definitions

Sperry Drilling Services

2007.1

Details Definitions

Directional Drilling

• • • • • • • • • •

Definitions

Directional Drilling Horizontal Well Extended Reach Drilling Measured Depth Survey Station distance Course Length Hole Inclination Hole Direction Vertical Depth, TVD Latitude & Departure

• • • • • • • • • •

Closure Target Closure Vertical Section Vertical Sect. Direction Dogleg Dogleg Severity Build/Drop/Turn Rate Survey at Bit Tortuosity Directional Difficulty Index

Sperry Drilling Services 2007

Controlled Directional Drilling

Well Profile Classes

The science of deviating a wellbore along a planned course to subsurface target whose location is at a given lateral distance and direction from the vertical, at a specified vertical depth. Drilling a wellbore with planned deviation from vertical to pre-determined target(s)

Long radius Medium radius Intermediate radius

2-6°/100 ft 6-35°/100 ft 35-65°/100 ft

Short radius

65-115°/100 ft

Ultra short radius

> 115°/100ft

target

Definition : Horizontal Well

• A directional well with a continuous section of wellbore with planned inclination > 86°

Extended Reach Drilling ERD • The drilling of a wellbore in which the final measured depth will be greater than twice the vertical depth MD > 2 TVD

MD

> 86°

TVD

Directional Drilling - Definitions

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Sperry Drilling Services

2007.1

Measured Depth “MD”

• The distance measured along the path of the wellbore from the surface depth reference to any point located on the path of the wellbore

Survey Station - SS

Any point (depth) along the wellbore at which a directional survey is taken

• Total depth (TD) is the measured depth from the surface depth reference to the bottom of the wellbore as measured along the path of the wellbore • More precisely it is the “along hole depth” (AHD)

Course Length - CL The measured length of the wellbore between any two survey stations

SS1

SS2

Hole Inclination or Drift Angle

The angle of inclination is measured between vertical and the tangent of the wellbore at a survey station

CL = MD2 - MD1 tangent survey station

P MD1 @ SS 1

vertical projection of the wellbore inclination

MD2 @ SS 2 vertical

Formation Dip Angle

Hole Direction Reference North

Horizontal

φ

downdip

P

horizontal projection of the wellbore survey station

tangent updip

Directional Drilling - Definitions

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Sperry Drilling Services

2007.1

Vertical Depth Increment - ΔTVD

True Vertical Depth - TVD • The sum of all the ΔTVDs calculated from surveys taken along the path of the wellbore from the surface depth reference (i = 1) to the point of interest (i = n)

The vertical distance between two horizontal planes containing survey stations

• The depth reference must always be given (e.g. 1230 ft TVD-RT)

1. survey station

n

TVD = ∑ ΔTVDi

course length

Δ TVD

i =1

2. survey station Note : the ΔTVD values are calculated from surveys

Latitude and Departure

Closure

N

Direction and distance of the last survey station relative to the first survey station. The direction is measured from the reference North as Azimuth.

Y

N

P

y

P

latitude

closure direction

E

x

departure

0

sur clo

W

X

target

e

E

S

Vertical Section (1) Target Closure Direction and distance of the target center relative to the first survey station

N

wellhead

Y

VS direction

TC

N

P closure direction

target re closu

W

E E

VS origin

X

Z

S

Directional Drilling - Definitions

TVD

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2007.1

Vertical Section - Plan

Vertical Section (2) N

Vertical Plot

Horizontal Plot

Y

Grid North

VS direction TC

Select : • VS Origin (default : surface location) • Direction (default : target center) KOP

P( x, y )

y le ng th

Calculate :

EOB

VS

• VS Length

EOB

x

VS origin

E

TC

X TVD

Vertical Section

VS direction

East

Note : scales might be different !

Vertical Section – Plan & Surveys Vertical Plot

Dogleg - DL

Horizontal Plot Grid North

The total 3 - dimensional change in hole direction and inclination between 2 survey stations, combined

TC

– expressed in degrees – for example :

KOP

DL = 7.0°

EOB

EOB TC

TVD

Vertical Section

VS direction

East

DLS and Radius of a Circle Dogleg Severity - DLS The total 3 - dimensional change in hole direction and inclination between 2 survey stations, combined, over a reference course length : change of angle DLS = course length

Change of angle : 360° Course length : 2R

π

R

- usually expressed in degrees per one hundred feet - for example : DLS = 7.0°/100 ft

DLS =

which is equivalent to 6.89°/30m or 2.30°/10m Conversion : (DLS deg/100ft) x 0.9840 = DLS deg/30m

Directional Drilling - Definitions

DLS =

360 2Rπ

× 100 =

5729.583 R

ft

≈

5730 R

(deg/100ft)

ft

360 × = 1718.875 ≈ 1719 ( 30 deg/30m) 2Rπ Rm Rm

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Sperry Drilling Services

2007.1

Build, Drop and Turn Rate

Build, Drop and Turn Rate

Again, change of angle over reference distance :

Build or Drop Rate Build/Drop Rate =

inclination change in degrees distance in feet

azimuth change in degrees distance in feet

ΔIN ΔL

X 100 [deg/100ft]

Turn Rate Turn Rate =

BUR =

TR =

Δ AZ ΔL

X 100 [deg/100ft]

X 100 [deg/100ft]

X 100 [deg/100ft]

Note : Turn rate is also referred as “walk” rate

Build, Drop and Turn Rate (DrillQuest)

Survey at Bit Definition : extrapolated values from survey depth to bit depth

INbit = IN +

BUR ×L 100

[deg]

TR ×L 100

[deg]

AZbit = AZ + IN AZ

Measured inclination, deg Measured direction, deg

L BUR TR

Bit-sensor distance, ft (m) Build or drop rate, deg/100ft (deg/30m) Turn rate, deg/100ft (deg/30m)

L

Tortuosity of Deviated Wells

Tortuosity

Definition : The actual pore space length over the straight path in the reservoir rock

Definition : The average excess DLS over plan

La actual

TOR =

straight

ΣDLsvy − ΣDLplan × 100 ΔMD svy

(deg/ 100 ft )

L Example :

tortuosity = La / L Source : SPE 23850

Directional Drilling - Definitions

TOR = (133.72 - 102.13)/ 596.0 x 100 = 5.3 (deg/100ft) Source : SPE 23850

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2007.1

Directional Difficulty Index (1)

Directional Difficulty Index (2)

Directional Drilling Difficulty Bands

DDI = log10 MD x AHD x TOR TVD

DDI < 6.0

Where : MD AHD TOR TVD

measured depth, ft along-hole displacement, ft tortuosity, true vertical depth, ft

Relatively short wells, simple profiles with low tortuosity

6.0 < DDI < 6.4

Either short wells with high tortuosity, or longer wells with lower tortuosity

6.4 < DDI < 6.8

Longer wells with relatively tortuous wellpaths

6.8 < DDI

Long tortuous well profiles with a high degree of difficulty

Note : DQ calculates DDI Source : IADC/SPE 59196

Source : IADC/SPE 59196

BULLETIN ON

DIRECTIONAL DRILLING SURVEY CALCULATION METHODS AND TERMINOLOGY

API Bulletin D20 First Edition December 31, 1985

Directional Drilling - Definitions

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