Directional Drilling and Deviation Control DRILLING ENGINEERING CHAPTER # 8 Directional Drilling and Deviation Control

Definition Directional Drilling: Deviation Control: X-Y Plane The process of directing the wellbore along some trajectory to a predetermined target. Deviation Control: The process of keeping the wellbore contained within some prescribed limits, relative to inclination angle, horizontal excursion from the vertical or both. X-Y Plane X – Plane = direction plane Y – Plane = inclination plane

Purpose of Directional Drilling Angles X-Y = Plane X – angle = direction angle Y-Z = Plane Y – angle = inclination angle Purpose of Directional Drilling Res. Under lake (economics, environmental reasons) Offshore drilling. Res. beneath population centers. Res. beneath natural obstruction (mountains) Or severe topographical features. Sidetracking out of an existing wellbore to bypass an obstruction (fish) or explore additional producing horizons in adjacent sectors. Relief well to plug a blow out.

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

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

Typical offshore development platform with directional wells

Developing a field under a city using directionally drilled wells

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

Sidetracking around a fish

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

7.1 Planning The Directional Well 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.

Types of Trajectories q1 < q3 < q2 < q4 Build and hold trajectory penetrates target at max. build-up angle. Build-hole and drop (s-shape) penetrate angle vertically Build-hold drop and/or hold (modified s-shape) penetrates target at angle less than max. inclination angle in the hold section. Continuous build trajectory inclination angle is increasing. q1 < q3 < q2 < q4

X3 = horizontal departure g1 = radius of curvature D3 = TVD true vertical depth D1 = kick off point TVD q = rate of inclination angle build up

Geometry of build-and-hold type well

7.2 Build and Hold Trajectory Circumference = 2pr S=rq q in radians max. inclination angle 1 radian = 180 o/p = 57.29578 o 1o = p/180 radians q = degrees per unit length = q/L = inclination angle build up rate q = 1o/100ft r = S /q r = radius of curvature

S = g q (8.1)

To find angle T look at triangle OBA (8.2) q = W - T To find angle T look at triangle OBA (8.3a) (8.3b) To find angle W consider triangle OBC (8.4)

CO = g1 (8.5) q = W - T

(8.6) Length of the arc section DC (buildup section) (8.7)

Length of CB (Trajectory Path) Straight at constant inclination angle can be determined from BCO Total measured depth DM for TVD of D3 is (8.8)

Horizontal departure at end of build up (8.9) True Vertical depth at end of build up section (8.12)

Geometry for the build section

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 (8.10) (8.11)

New measured depth for any part of the build up (8.13) New measured depth at TVD of (D*< D3)(D2<D*< D3) (8.16) Horizontal Departure X* (X2<X*< X3) (8.18)

For r1 < X3 (8.20)

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

Directional quadrants and compass measurements

Vertical calculation

Horizontal calculation

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

Techniques for making a positive direction change

7.3 Directional 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

Directional drilling applications

Stabilizing tool

The use of stabilizers in directional drilling

Other Application of Stabilizing Tools Key seat Guide Avoidance of Pressure Differential Sticking Whip stock Knuckle Joint

Whip stocks

Knuckle joint

Using a section mill to prepare for a kick-off

Jetting bit

Jetting a trajectory change

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