Directional borehole drilling system and method

• US 20020112887A1
• Filed: 02/20/2002
• Published: 08/22/2002
• Est. Priority Date: 02/20/2001
• Status: Active Grant

• Current Assignee: Harrison, William H.
• Original Assignee: Harrison, William H.
• Inventors: Harrison, William H.
• Granted Patent: US 6,691,804 B2
• Time in Patent Office: Days
• US Class Current: 175/27
• CPC Class Codes: E21B 10/246 with pumping means for feeding lubricant
• CPC Class Codes: E21B 7/04 Directional drilling
• CPC Class Codes: E21B 7/064 specially adapted drill bits therefor

Abstract

A directional borehole drilling system employs a controllable drill bit, which includes one or more conical drilling surfaces. Instrumentation located near the bit measures present position when the bit is static, and dynamic toolface when the bit is rotating. This data is processed to determine the error between the present position and a desired trajectory, and the position of one or more of the bit'"'"'s cones is automatically changed as needed to make the bit bore in the direction necessary to reduce the error. The controllable drill bit preferably comprises three cone assemblies mounted about the bit'"'"'s central axis, each of which includes a leg with “toed-out” axle. In response to a command signal, a cone translates along the axle to cause it to bear more of the bit weight, thus excavating more deeply over the commanded toolface sector and causing the bit to bore in a preferred direction.

Claims

1. A directional borehole drilling system, comprising:

at least one sonde for mounting within a drill string which is coupled to a controllable drill bit, said at least one sonde comprising;

a storage medium that contains information that represents a desired drill bit trajectory,

instrumentation that determines the present position and attitude angles of said bit when said bit is in a static position, and the bit'"'"'s toolface angle when said bit is rotating, and

a processor that receives said present position and dynamic toolface information from said instrumentation, determines the error between said present position and said desired trajectory, and provides said command signals to said controllable drill bit such that said drill bit bores in the direction necessary to reduce said error,

said controllable drill bit comprising;

a plurality of cone assemblies mounted about a central axis, each of which includes a cone which rotates about a respective axle and thereby drills a borehole when said bit is driven to rotate about said central axis, each cone assembly having a leg which is attached to a common frame and having its axle “

toed out”

such that the rolling cone exerts a radial force on the leg, and

at least one mechanism coupled to respective ones of said cone assemblies that is actuated in response to a respective one of said command signals, said at least one mechanism arranged to force its respective cone to translate along its axle when actuated while allowing it to continue to rotate about its axle, and to allow its respective cone to be seated snugly against a thrust washer between it and said leg when not actuated while allowing it to continue to rotate about its axle.

2. The borehole drilling system of claim 1, wherein the axle of each leg of each cone assembly is “

toed-out”

by approximately five degrees.

3. The borehole drilling system of claim 1, wherein said controllable drill bit comprises three cone assemblies mounted about said central axis and three of said mechanisms coupled to respective ones of said cone assemblies.

4. The borehole drilling system of claim 1, wherein each of said mechanisms comprises:

a means for translating said mechanism'"'"'s respective cone along said axle of said cone assembly, and

a means for retaining said cone such that, when said cone is translated along its axle, it is restrained to a prescribed length of travel.

5. The borehole drilling system of claim 4, wherein said means for translating said cone comprises filling a closed cavity between said leg and the backside of said cone with pressurized hydraulic fluid when cone translation is commanded.

6. The borehole drilling system of claim 5, further comprising a fluid seal between said leg and said cone to retain said fluid within said cavity.

7. The borehole drilling system of claim 6, further comprising an electro-hydraulic valve to direct said pressurized hydraulic fluid upon command to fill said cavity and cause translation of said cone, and to direct said pressurized hydraulic fluid upon command out of said cavity allowing said cone to reset to its non-translated state.

8. The borehole drilling system of claim 7, further comprising a hydraulic accumulator to store said pressurized hydraulic fluid that is supplied to said electro-hydraulic valve.

9. The borehole drilling system of claim 7, further comprising a journal bearing existent between said cone and said axle and which is lubricated by said pressurized hydraulic fluid, said hydraulic accumulator arranged to store said pressurized hydraulic fluid that is supplied to the journal bearing.

10. The borehole drilling system of claim 8, further comprising a positive displacement hydraulic pump that pumps said hydraulic fluid from a low pressure state to a high pressure state to be stored in said accumulator.

11. The borehole drilling system of claim 10, further comprising a pump assembly having at least one cylinder, a piston and two check valves located in a bore centered in said axle.

12. The borehole drilling system of claim 11, further comprising a face cam located and affixed to the bottom of said cone in its axle bore such that rotation of said cone causes said piston to reciprocate and said fluid to be pumped.

13. The borehole drilling system of claim 1, wherein said instrumentation which determines present position and attitude angles comprises a plurality of accelerometers, a plurality of magnetometers, and a means for determining the length of pipe which has been added to the top end of said drill string since the previous determination of present position and attitude angles.

14. The borehole drilling system of claim 13, further comprising a transmitter located near the end of said drill string opposite said controllable drill bit with which the length of pipe added to said drill string is transmitted to said sonde, said means for determining the length of pipe added to said drill string comprising a receiver which receives said pipe length data from said transmitter.

15. The borehole drilling system of claim 14, wherein said storage medium is coupled to said receiver and said desired drill bit trajectory information is conveyed to said storage medium via said transmitter and receiver.

16. The borehole drilling system of claim 1, wherein said desired drill bit trajectory is preloaded into said storage medium.

18. The borehole drilling system of claim 17, wherein said driving means comprises a motor mechanically coupled to said drill string at the end of said drill string opposite said controllable drill bit.

19. The borehole drilling system of claim 17, wherein said driving means comprises a mud motor coupled to said controllable bit.

20. The borehole drilling system of claim 17, wherein each of said mechanisms comprises:

a closed cavity formed between the backside of the cone of said mechanism'"'"'s respective cone assembly, its leg and its axle, wherein hydraulic fluid may be injected to cause said cone to translate along said axle when actuated and to allow its respective cone to rest against its leg when not actuated,

an electro-hydraulic valve assembly mounted in said leg,

a hydraulic accumulator located within said leg,

a journal bearing existent between the cone and its axle, and

a positive displacement hydraulic pump located within a bore in the center of said axle, said pump pressurizing hydraulic fluid stored in said accumulator to lubricate said journal bearing.

17. A directional borehole drilling system, comprising:

a controllable drill bit, said bit comprising;

a plurality of cone assemblies mounted about a central axis, each of which includes a cone that rotates about a respective axle and thereby drills a borehole when said bit is driven to rotate about said central axis, each cone assembly having a leg which is attached to a common frame and having its axle “

toed out”

such that the rolling cone exerts a radial force on the leg, and

at least one mechanism coupled to respective ones of said cone assemblies that is actuated in response to a respective command signal, said at least one mechanism arranged to force its respective cone to translate along its axle when actuated while allowing it to continue to rotate about its axle, and to allow its respective cone to be seated snugly against a thrust washer between it and said leg when not actuated while allowing it to continue to rotate about its axle,

a drill string coupled to said controllable drill bit,

a driving means coupled to said drill string that drives said bit to rotate about said central axis, and

at least one sonde within said drill string that comprises;

a storage medium that contains information that represents a desired drill bit trajectory,

a first instrumentation package that determines the present position and attitude angles of said bit when said bit is in a static position,

a second instrumentation package that determines the dynamic toolface angle of said bit and the positions of the cone assemblies coupled to said mechanisms when said bit is rotating about said central axis, and

a processor that receives said present position and attitude angles and cone assembly position information from said instrumentation, determines the error between said present position and said desired trajectory, and provides said command signals to said controllable drill bit such that said drill bit bores in the direction necessary to reduce said error.

21. A method of directional drilling in a borehole, comprising the steps of:

providing a controllable drill bit that comprises a plurality of cone assemblies mounted about a central axis, each of which includes a cone that rotates about a respective axle and can be made to translate or remain seated against a leg which is attached to a common frame,

determining a desired trajectory for said drill bit,

determining the present position of said drill bit,

determining the error between said present position and said desired trajectory,

rotating said drill bit about said central axis,

determining the dynamic toolface angle of said bit, and causing, based on said present position, said dynamic toolface angle and at least one of said cones to translate along its axle such that said drill bit bores in a direction necessary to reduce said error.

22. The method of claim 21, wherein said controllable drill bit includes respective mechanisms coupled to respective ones of said cone assemblies, each of said mechanisms comprising:

a closed cavity formed between the backside of the cone of said mechanism'"'"'s respective cone assembly, its leg and its axle, wherein hydraulic fluid may be injected to cause said cone to translate along said axle when actuated and to allow its respective cone to rest against its leg when not actuated,

an electro-hydraulic valve assembly mounted in said leg,

a hydraulic accumulator located within said leg,

a journal bearing existent between the cone and its axle, and

a positive displacement hydraulic pump located within a bore in the center of said axle, said pump pressurizing hydraulic fluid stored in said accumulator to lubricate said journal bearing.

23. A controllable drill bit comprising:

a plurality of cone assemblies mounted about a central axis, each of which includes a cone that rotates about a respective axle as said bit is rotated about said central axis and can be made to translate or be seated against a leg which is attached to a common frame,

a plurality of mechanisms coupled to respective ones of said cone assemblies, each of which is actuated in response to a respective command signal, each mechanism arranged to force its respective cone assembly to translate along its axle when actuated and to allow its respective cone assembly to rest against it leg when not actuated, each of said mechanisms comprising;

a closed cavity formed between the backside of the cone of said mechanism'"'"'s respective cone assembly, its leg and its axle, wherein hydraulic fluid may be injected to cause said cone to translate along said axle when actuated and to allow its respective cone to rest against its leg when not actuated,

an electro-hydraulic valve assembly mounted in said leg,

a hydraulic accumulator located within said leg,

a journal bearing existent between the cone and its axle, and

a positive displacement hydraulic pump located within a bore in the center of said axle, said pump pressurizing hydraulic fluid stored in said accumulator to lubricate said journal bearing.