Directional Horizontal Drilling

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3. Directional Drilling There's a maxim in drilling that says "there's no such thing as a straight hole." All wells, whether by accident or by design, exhibit changes in hole angle and direction. Crooked hole tendencies were considered early as a serious drawback to the widespread use of rotary rigs. But the benefits of rotary drilling were more than sufficient to overcome this perceived limitation So the industry began developing ways to keep wells on course. Thus was born the science or, perhaps more accurately, the art of deviation control.

4. Definition of Directional Drilling Directional drilling can be defined as “ Science of directing a wellbore along a predetermined trajectory to intersect a subsurface target”.

5. Applications of Directional Drilling

6. Applications of Directional Drilling Offshore Multi-well Drilling Relief Wells Inaccessible Locations Fault Controlling Salt Dome Drilling Sidetracking Horizontal Wells Controlling Vertical Wells Horizontal Wells

7. Offshore Multi-well Drilling

8. Relief Wells Objective is to intercept the borehole of a well for killing purpose These wells are deviated to pass as close as possible to the uncontrolled wells Heavy mud is pumped into the reservoir to overcome the pressure and bring the wild well under control

9. Inaccessible Locations For targets located beneath city, river etc Directional well is drilled to reach the target

10. Fault Drilling Bits change direction due to faulted subsurface formations Faults can slip and shear the casing

11. Salt Dome Drilling Severe drilling problems while drilling through salt formations Directional well is drilled to reach the reservoir, thus avoiding the problems associated to drilling salt dome Another solution is to use salt saturated mud

12. Sidetracking Objective is to get past a fish or to sidetrack a dry hole to more promising target or to explore the extent of a producing zone in a certain sector of a field

13. Controlling Vertical Wells Directional wells are drilled to straighten vertical wells

14. Horizontal Wells Increase productivity of various formations More exposure to the reservoir

15. Types of Directional Wells Type 1: Build and Hold -- this pattern employs a shallow initial deflection and a straight-angle approach to the target. Its used to reach single targets at moderate depths, and sometimes for drilling deeper wells with large horizontal departures. Type 2: Build, Hold and Drop -- after a relatively shallow deflection, this pattern holds angle until the well has reached most of its required horizontal displacement. This pattern is most applicable to wells exposing multiple pay zones, or wells subject to target or lease boundary restrictions.

16. Types of Directional Wells Type 3: Continuous Build -- unlike the Type 1 and 2 patterns, this trajectory has a relatively deep initial deflection, after which angle is maintained to the target. The continuous build pattern is well-suited to salt-dome drilling, fault drilling, sidetrack sand redrills. Type 4: Build, Hold and Build -- this is the general pattern describing horizontal wells. The decision to drill horizontally is primarily based on reservoir engineering and reservoir management considerations.

17. Deflection Tools Downhole Mud Motors Directional wedges Jet bits with oriented nozzles

18. Deviation in Vertical Wells - Causes Following are the contributing factors for wellbore deviation Formation - Type, lithology - Anisotropy Bottom hole assembly size, configuration - Stabilizers size, type & positioning - Drill collars & Reamers Drilling parameters - Weight on bit - Hydraulics Bit type & Design features

19. Deviation Control Methods Wellbore deviation can be controlled by Using pendulum assembly, consisting of the bit, drill collars and strategically positioned stabilizers, to decrease hole angle (i.e., straighten the hole) Using packed hole assemblies, consisting of reamers, short collars and stabilizers, or square drill collars, to "lock in" the bit and maintain a constant hole angle Using directional drilling tools (e.g., downhole motors with bent housings)

20. Horizontal Drilling Horizontal drilling is the process of directing part of a well course through a reservoir such that its inclination angle is approximately 90° from vertical Horizontal section may be anywhere from a few feet to thousands of feet in length. Horizontal drilling begins with a more-or-less vertical surface section, followed by a bend section which progresses from approximately 0° to 90° inclination with depth, and finally by a horizontal or lateral section

21. Horizontal Drilling Applications Reservoirs that would otherwise be economically inaccessible For new development wells Enhanced oil recovery

22. Well Configuration

23. Well Configuration Short radius build rate between 1o and 3o degrees per foot build radius 50 feet or less Applications infill drilling in depleted reservoirs shaly intervals or other trouble-prone formations multiple drain holes enhanced oil recovery Ultra-short radius no bend section Applications soft, unconsolidated formations multiple drain holes from existing vertical wells