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CHAPTER # 8

DRILLING ENGINEERING. CHAPTER # 8. Directional Drilling and Deviation Control. Definition. Directional Drilling: The process of directing the wellbore along some trajectory to a predetermined target. Deviation Control:

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CHAPTER # 8

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

  2. Definition Directional Drilling: 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

  3. 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.

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

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

  6. Typical offshore development platform with directional wells

  7. Developing a field under a city using directionally drilled wells

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

  9. Sidetracking around a fish

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

  11. 7.1 Planning The Directional Well Trajectory 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.

  12. Types of Trajectories • 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

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

  14. Geometry of build-and-hold type well

  15. 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

  16. S = g q (8.1)

  17. (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)

  18. CO = g1 (8.5) • q = W - T

  19. (8.6) Length of the arc section DC (buildup section) (8.7)

  20. 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)

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

  22. Geometry for the build section

  23. 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)

  24. (8.13) New measured depth for any part of the build up New measured depth at TVD of (D*< D3)(D2<D*< D3) (8.16) Horizontal Departure X* (X2<X*< X3) (8.18)

  25. For r1 < X3 (8.20)

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

  27. Directional quadrants and compass measurements

  28. Vertical calculation

  29. Horizontal calculation

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

  31. Techniques for making a positive direction change

  32. 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

  33. Directional drilling applications

  34. Stabilizing tool

  35. The use of stabilizers in directional drilling

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

  37. Whip stocks

  38. Knuckle joint

  39. Using a section mill to prepare for a kick-off

  40. Jetting bit

  41. Jetting a trajectory change

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

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