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CHAPTER # 8CHAPTER # 8

Directional Drilling and Directional Drilling and Deviation ControlDeviation Control

DRILLING ENGINEERINGDRILLING ENGINEERING

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DefinitionDefinition

Directional Drilling:Directional Drilling: The process of directing the wellbore along some trajectory to a The process of directing the wellbore along some trajectory to a predetermined target.predetermined target.

Deviation Control:Deviation Control: The process of keeping the wellbore contained within some The process of keeping the wellbore contained within some prescribed limits, relative to inclination angle, horizontal excursion prescribed limits, relative to inclination angle, horizontal excursion from the vertical or both.from the vertical or both.

X-Y PlaneX-Y Plane X – Plane = direction planeX – Plane = direction plane Y – Plane = inclination planeY – Plane = inclination plane

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AnglesAngles

X-Y = Plane X – angle = direction angleX-Y = Plane X – angle = direction angle Y-Z = Plane Y – angle = inclination angleY-Z = Plane Y – angle = inclination angle

Purpose of Directional DrillingPurpose of Directional Drilling

Res. Under lake (economics, environmental reasons)Res. Under lake (economics, environmental reasons) Offshore drilling.Offshore drilling. Res. beneath population centers.Res. beneath population centers. Res. beneath natural obstruction (mountains) Or severe Res. beneath natural obstruction (mountains) Or severe

topographical features.topographical features. Sidetracking out of an existing wellbore to bypass an Sidetracking out of an existing wellbore to bypass an

obstruction (fish) or explore additional producing horizons in obstruction (fish) or explore additional producing horizons in adjacent sectors.adjacent sectors.

Relief well to plug a blow out.Relief well to plug a blow out.

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Inclination and direction planes as a wellbore proceeds in Inclination and direction planes as a wellbore proceeds in the depth plane.the depth plane.

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Plan view of a typical oil and gas structure under a lakePlan view of a typical oil and gas structure under a lake

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Typical offshore development platform with directional Typical offshore development platform with directional wellswells

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Developing a field under a city using directionally drilled Developing a field under a city using directionally drilled wellswells

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Drilling of directional wells where the reservoir is Drilling of directional wells where the reservoir is beneath a major surface obstructionbeneath a major surface obstruction

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Sidetracking around a fishSidetracking around a fish

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Using an old well to explore for new oil by sidetracking Using an old well to explore for new oil by sidetracking out of the casing and drilling occasionallyout of the casing and drilling occasionally

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7.17.1 Planning The Directional Well Planning The Directional Well TrajectoryTrajectory

Trajectory

Well path that will intersect given target.

First design propose the various types of paths that can be drilled economically.

Second includes effects of geology on the bottomhole assemblies (BHA) and other factors that could influence the final wellbore trajectory.

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Types of TrajectoriesTypes of Trajectories

Build and hold trajectory penetrates target at max. build-Build and hold trajectory penetrates target at max. build-up angle.up angle.

Build-hole and drop (s-shape) penetrate angle verticallyBuild-hole and drop (s-shape) penetrate angle vertically

Build-hold drop and/or hold (modified s-shape) penetrates Build-hold drop and/or hold (modified s-shape) penetrates target at angle less than max. inclination angle in the hold target at angle less than max. inclination angle in the hold section.section.

Continuous build trajectory inclination angle is increasing.Continuous build trajectory inclination angle is increasing.

1 1 < < 3 3 < < 2 2 < < 4 4

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X3 = horizontal departure

= radius of curvature

D3 = TVD true vertical depth

D1 = kick off point TVD

q = rate of inclination angle build up

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Geometry of build-and-hold type wellGeometry of build-and-hold type well

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7.27.2 Build and Hold TrajectoryBuild and Hold Trajectory

Circumference = Circumference = rr S=rS=r n radians max. inclination anglen radians max. inclination angle 1 radian = 1801 radian = 180 o o// = 57.29578 = 57.29578 o o

11oo = = /180 radians/180 radians q = degrees per unit length = q = degrees per unit length = /L/L

= inclination angle build up rate= inclination angle build up rate q = 1q = 1oo/100ft /100ft

r = S /r = S / r = radius of curvaturer = radius of curvature

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S =

qlength

rees

S

deg1

rees

length

q deg

1

180

deg

1

rees

length

q

11

1801180qor

q(8.1)(8.1)

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= T

To find angle T look at triangle OBA

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31tanDD

X

AO

BAT

13

31arctanDD

XT

To find angle consider triangle OBC

BO

COSin

(8.2)(8.2)

(8.3a)(8.3a)

(8.3b)(8.3b)

(8.4)(8.4)

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CO = CO =

22 )()( BAOABO

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213 )()( XDDBO

213

231

1

)()( DDXSin

213

231

1

)()(arcsin

DDX

= T

(8.5)(8.5)

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13

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213

231

1 arctan)()(

arcsinDD

X

DDX

Length of the arc section DC (buildup section)Length of the arc section DC (buildup section)

(8.6)(8.6)

1801

rDC

qDC

qr

1

1801

(8.7)(8.7)

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Length of CB (Trajectory Path)Straight at constant inclination angle can be determined from BCO

tan

tan

1

1

rCB

CB

r

CB

CO

Total measured depth DM for TVD of D3 is

tan1

1

r

qDDm

(8.8)(8.8)

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Horizontal departure at end of build up

)cos1(cos 1112

2

rrrX

OCDconsiderECX

(8.9)(8.9)

True Vertical depth at end of build up section

sin112 rDD (8.12)(8.12)

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Geometry for the build sectionGeometry for the build section

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Measure depth and Horizontal departure before reaching maximum angle along any part of build up.

Consider intermediate inclination angle

XN=Horizontal Departure at C

DN=Vertical depth

Consider DOC

)cos1(

cos

sin

11

11

11

rX

rrX

rDD

N

N

N

(8.11)(8.11)

(8.10)(8.10)

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New measured depth for any part of the build upNew measured depth for any part of the build up

qDDMN

1

New measured depth at TVD of (DNew measured depth at TVD of (D**< D< D33)(D)(D22<D<D**< D< D33))

cos

sin111

rDD

qDDMP

(8.13)(8.13)

(8.16)(8.16)

Horizontal Departure XHorizontal Departure X** (X (X22<X<X**< X< X33))

tan)sin()cos1( 11 rDDrX (8.18)(8.18)

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For r1 < X3

)(sin

)()(180

13

13

13

1

13

13

rX

DDarcTan

DD

rarcCos

rX

DDarcTan

(8.20)(8.20)

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Build-hold-and-drop and hold (modified-S)Build-hold-and-drop and hold (modified-S)

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Directional quadrants and compass measurementsDirectional quadrants and compass measurements

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Vertical calculationVertical calculation

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Horizontal calculationHorizontal calculation

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Three-dimensional view of a wellbore showing components that Three-dimensional view of a wellbore showing components that comprise the X, Y and Z parts of the trajectorycomprise the X, Y and Z parts of the trajectory

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Techniques for making a positive direction changeTechniques for making a positive direction change

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7.37.3 Directional Drilling ToolsDirectional Drilling Tools

Stabilizing Tools The Stiff Hook-Up The Pendulum Hook-Up Angle Building Hook-Ups The Lock-in Hook-Ups Angle Losing Hook-Ups

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Directional drilling applicationsDirectional drilling applications

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Stabilizing toolStabilizing tool

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The use of stabilizers in directional drillingThe use of stabilizers in directional drilling

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Other Application of Stabilizing ToolsOther Application of Stabilizing Tools

Key seat Guide Avoidance of Pressure Differential Sticking Whip stock Knuckle Joint

37Whip stocksWhip stocks

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Knuckle jointKnuckle joint

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Using a section mill to prepare for a kick-offUsing a section mill to prepare for a kick-off

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Jetting bitJetting bit

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Jetting a trajectory changeJetting a trajectory change

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Fig 8.95: A typical positive-displacement mud motor Fig 8.95: A typical positive-displacement mud motor (PDM)(PDM)