Claims
- 1. A rotary directional drilling tool apparatus, comprising: a drive shaft having a drill bit on one end thereof, said bit and shaft having a first axis of rotation; a tubular housing having a second axis of rotation and adapted to be rotated by a drill string; universal joint means for connecting said drive shaft to said housing and transmitting torque from said housing to said drive shaft and said bit; gravity responsive means for holding said first axis so that said bit faces in one direction in space during rotation of said housing about said second axis, said holding means including normally disengaged clutch means; and means for engaging said clutch means.
- 2. The apparatus of claim 1 wherein said holding means includes upper and lower mandrels mounted in said housing, said lower mandrel being movable longitudinally therein; means on said lower mandrel for aligning said axes in one position and for misaligning said axes in another position; and index means on said lower mandrel and said housing for controlling said longitudinal positions.
- 3. The apparatus of claim 2 wherein said clutch means includes a slidable spline connection on said upper and lower mandrels that is disengaged in said one position and engaged in said other position to correspondingly uncouple and couple said gravity responsive means from and to said lower mandrel.
- 4. The apparatus of claim 3 wherein said engaging means includes hydraulically operable means comprising flow passage means in said lower mandrel for causing a pressure drop that forces said lower mandrel toward said other position where said axes are misaligned; and resilient means for forcing said lower mandrel toward said one position where said axes are aligned.
- 5. The apparatus of claim 4 further including lock means for orienting said lower mandrel in a certain rotational position relative to said housing when said lower mandrel is in said one position to enable the toolface of said bit to be set by turning the drill string.
- 6. The apparatus of claim 2 wherein said aligning and misaligning means includes a coupling member on the lower end of said lower mandrel, said coupling member having a bore that is inclined relative to said second axis, said drive shaft having pivotal joint means engaged in said bore so that said first axis is tilted about said universal joint means and relative to said second axis in response to said longitudinal movement.
- 7. The apparatus of claim 2 wherein said index means includes a sleeve mounted on said lower mandrel, said sleeve having inclined groove means extending between longitudinally spaced levels thereon, and pin means on said housing and cooperating with said groove means and levels to define the limits of said longitudinal movement.
- 8. The apparatus of claim 4 wherein said flow passage means includes a plurality of flow ports arranged such that drilling fluids flowing through said apparatus pass through all of said flow ports in said one position and less than all of said flow ports in said other position to provide an indication at the earth's surface of the longitudinal position of said lower mandrel.
- 9. A method of drilling a directional borehole with a drill bit mounted on the lower end of a rotary drill string by an articulated drive shaft, said drill string having a first axis of rotation and said drive shaft and bit having a second axis of rotation, comprising the steps of: transmitting torque from said drill string to said drive shaft and bit with said second axis intersecting said first axis at a low angle so that said borehole is drilled on a curved trajectory; employing gravity to maintain said second axis pointed in one direction in space during rotation of said bit by said drill string; pumping drilling fluid down said drill string; temporarily stopping and then resuming said pumping step; and in response to said stopping and resuming steps, aligning said axes so that the drilling will proceed straight ahead.
- 10. The method of claim 9 including the further step of rotationally orienting said drill string while said axes are aligned so that said drive shaft and bit will have a selected toolface when directional drilling is resumed.
- 11. The method of claim 10 including the further steps of temporarily stopping and then resuming said pumping step; and in response to said last-mentioned stopping and resuming steps, misaligning said axes to enable said bit to drill the borehole on a curved trajectory.
- 12. The method of claim 9 including the further step of obviating said employing step while said axes are aligned.
RELATED APPLICATION
This application is a continuation-in-part of application Ser. No. 08/286,291, filed Aug. 5, 1994, now U.S. Pat. No. 5,484,029.
US Referenced Citations (28)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2246151 |
Jan 1992 |
GBX |
Non-Patent Literature Citations (1)
Entry |
Anadrill Schlumberger Brochure, "Anadrill Tightens Directional Control with Downhole-Adjustable Stabilizers", no date. |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
286291 |
Aug 1994 |
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