Long reach rotary drilling assembly

• US 6,467,557 B1
• Filed: 07/31/2000
• Issued: 10/22/2002
• Est. Priority Date: 12/18/1998
• Status: Expired due to Term

• Current Assignee: WWT North America Holdings, Inc.
• Original Assignee: Western Oiltools Ltd.
• Inventors: Bloom, Duane T., Moore, N. Bruce, Beaufort, Ronald E., Krueger, R. Ernst
• Primary Examiner(s): Bagnell, David
• Assistant Examiner(s): GAY, JENNIFER HAWKINS
• Application Number:
  US09/629,493
• Time in Patent Office: 813 Days
• Field of Search: 175/51, 175/97, 175/98, 175/99, 175/45, 175/61, 175/320, 175/40, 175/74, 175/26, 175/50, 175/73, 299/31, 731/524.3, 731/524.5, 731/524.6, 731/525.1, 166/250.01, 166/255.1, 166/255.2, 166/65.1, 166/50, 166/117.5, 166/153
• US Class Current: 175/45
• CPC Class Codes: E21B 23/001 Self-propelling systems or apparatus, e.g. for moving tools within the horizontal portion of a borehole
• CPC Class Codes: E21B 23/08 Introducing or running tools by fluid pressure, e.g. through-the-flow-line tool systems
• CPC Class Codes: E21B 4/18 Anchoring or feeding in the borehole
• CPC Class Codes: E21B 44/005 Below-ground automatic control systems
• CPC Class Codes: E21B 7/062 the tool shaft rotating inside a non-rotating guide travelling with the shaft E21B7/067 and E21B7/068 take precedence
• CPC Class Codes: E21B 7/068 drilled by a down-hole drilling motor down-hole drives per se E21B4/00, E21B7/067 takes precedence

Abstract

A long reach rotary drilling assembly comprises an elongated conduit extending through a bore in an underground formation, a drill bit for being rotated to drill the bore, a 3-D steering tool on the conduit for steering the drill bit, and a tractor on the conduit for applying force to the drill bit. The steering tool includes a telemetry section, a rotary section, and a flex section assembled as an integrated system in series along the length of the tool. The flex section comprises a flexible drive shaft to which a bending force is applied when making inclination angle adjustments. The rotary section includes a deflection housing which rotates for making azimuth angle adjustments. The telemetry section receives inclination and azimuth angle steering commands together with actual inclination and azimuth angle feedback signals for controlling operation of the flex section and rotary section to steer the drilling assembly along a desired course. The tractor includes a gripper which can assume a first position that engages an inner surface of the bore and limits relative movement of the gripper relative to the inner surface. The gripper can also assume a second position that permits substantially free relative movement between the gripper and the inner surface of the bore. A propulsion assembly moves the tractor with respect to the gripper while the gripper portion is in the first position. The tractor applies force to the drill bit for drilling the bore along a desired course the direction of which is controlled by the 3-D steering tool.

Claims

1. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course;

the 3-D steering tool comprising a rotary section and a flex section;

in which the flex section includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the rotary section is coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor.

2. Apparatus according to claim 1 in which the telemetry section for the 3-D steering tool comprises mud pulse telemetry, and in which the propulsion assembly for the tractor comprises mud pulse telemetry for regulating pressure and/or flow of fluid within the tractor.

3. Apparatus according to claim 1 in which the telemetry section for the 3-D steering tool comprises an integral electrical wire telemetry system, and in which signals to the onboard controller for the tractor are delivered via the integral electrical wire telemetry system.

4. Apparatus according to claim 1 including a measurement-while-drilling tool for providing drill bit positional information to the controls for the steering tool.

5. Apparatus according to claim 1 in which the drilling tractor comprises:

a tractor body having a plurality of thrust receiving portions;

at least one valve on said tractor body positioned along at least one of a plurality of fluid flow paths between a source of fluid and said thrust receiving portions;

a plurality of grippers, each of said plurality of grippers being longitudinally movably engaged with said body, each of said plurality of grippers having an actuated position in which said gripper limits movement of said gripper relative to an inner surface of said borehole and a retracted position in which said gripper permits substantially free relative movement of said gripper relative to said inner surface, said plurality of grippers, said plurality of thrust receiving portions and said valves being configured such said tractor can propel itself at a sustained rate of less than 50 feet per hour and at a sustained rate of greater than 100 feet per hour.

6. Apparatus according to claim 1 in which the drilling tractor comprises:

a tractor body having a thrust-receiving portion having a rear surface and a front surface;

a spool valve comprising;

a valve body having a spool passage defining a spool axis, said valve body having fluid ports which communicate with said spool passage; and

an elongated spool received within said spool passage and movable along said spool axis to control flowrates along fluid flow paths through said fluid ports and said spool passage, said spool having a first position range in which said valve permits fluid flow from a fluid source to said rear surface of said thrust-receiving portion and blocks fluid flow to said front surface, the flowrate of said fluid flow to said rear surface varying depending upon the position of said spool within said first position range, said fluid flow to said rear surface delivering downhole thrust to said body, the magnitude of said downhole thrust depending on the flowrate of said fluid flow to said rear surface, said spool having a second position range in which said valve permits fluid flow from said fluid source to said front surface of said thrust-receiving portion and blocks fluid flow to said rear surface, the flowrate of said fluid flow to said front surface varying depending upon the position of said spool within said second position range, said fluid flow to said front surface delivering uphole thrust to said body, the magnitude of said uphole thrust depending on the flowrate of said fluid flow to said front surface;

a motor on said tractor body;

a coupler connecting said motor and said spool so that operation of said motor causes said spool to move along said spool axis; and

a gripper longitudinally movably engaged with said tractor body, said gripper having an actuated position in which said gripper limits movement of said gripper relative to an inner surface of said borehole and a retracted position in which said gripper permits substantially free relative movement of said gripper relative to said inner surface;

wherein said motor is operable to move said spool along said spool axis sufficiently fast to alter the net thrust received by said thrust-receiving portion by 100 pounds within 2 seconds.

7. Apparatus according to claim 6, wherein said sensors include a first pressure sensor configured to measure fluid pressure on said rear side of said thrust-receiving portion of said tractor body, and a second pressure sensor configured to measure fluid pressure on said front side of said thrust-receiving portion.

8. Apparatus according to claim 6, wherein said sensors include a displacement sensor configured to measure the position of said thrust-receiving portion with respect to said gripper.

9. Apparatus according to claim 6, wherein said sensors include a rotary accelerometer configured to measure the angular velocity of said output shaft.

10. Apparatus according to claim 6, wherein said sensors include a potentiometer configured to measure the rotational position of said output shaft.

11. Apparatus according to claim 1, in which the drilling tractor comprises:

a body;

a valve on said body, said valve being positioned along a fluid flow path from a source of a first fluid to a thrust-receiving portion of said body, said valve being movable generally along a valve axis, said valve having a first position in which said valve completely blocks fluid flow along said flow path and a second position in which said valve permits fluid flow along said flow path;

a motor on said body;

a coupler connecting said motor and said valve so that operation of said motor causes said valve to move along said valve axis; and

a pressure compensation piston exposed on a first side to said first fluid and on a second side to a second fluid, said first and second fluids being fluidly separate, said piston configured to move in response to pressure forces from said first and second fluids so as to effectively equalize the pressure of said first and second fluids;

wherein said valve is exposed to said first fluid, said motor being exposed to said second fluid.

12. Apparatus according to claim 1, in which the drilling tractor comprises:

an elongated body configured to pull equipment within said borehole,

said equipment exerting a longitudinal load on said body;

a gripper longitudinally movably engaged with said body, said gripper having an actuated position in which said gripper limits movement between said gripper and an inner surface of said borehole, and a retracted position in which said gripper permits substantially free relative movement between said gripper and said inner surface; and

a propulsion system on said body for propelling said body through said borehole while said gripper is in said actuated position;

wherein said body is sufficiently flexible such that said tractor can turn up to 80°

per 100 feet of travel, while said longitudinal load is at least 50-30,000 pounds.

13. Apparatus according to claim 12, wherein said body is sufficiently flexible such that said tractor can turn up to 45°

per 100 feet of travel, while said longitudinal load is at least 50-30,000 pounds.

14. Apparatus according to claim 12, wherein said body is sufficiently flexible such that said tractor can turn up to 600 per 100 feet of travel, while said longitudinal load is at least 50-30,000 pounds.

15. Apparatus according to claim 1, including a set of two or more connected tractors for moving within the borehole, comprising a logic component and said tractors, each of said tractors comprising:

an elongated tractor body having first and second thrust-receiving portions, each thrust receiving portion having a first surface and a second surface generally opposing said first surface;

a first gripper longitudinally movable with respect to said first thrust-receiving portion, said first gripper having an actuated position in which said first gripper limits movement of said first gripper relative to an inner surface of said borehole and a retracted position in which said first gripper permits substantially free relative movement between said first gripper and said inner surface;

a second gripper longitudinally movable with respect to said second thrust-receiving portion, said second gripper having an actuated position in which said second gripper limits movement of said second gripper relative to said inner surface and a retracted position in which said second gripper permits substantially free relative movement between said second gripper and said inner surface;

one or more valves on said tractor body controlling;

a first flowrate, said first flowrate being the flowrate of fluid flowing to and imparting thrust to said first surface of said first thrust-receiving portion;

a second flowrate, said second flowrate being the flowrate of fluid flowing to and providing thrust to said second surface of said first thrust-receiving portion;

a third flowrate, said third flowrate being the flowrate of fluid flowing to and providing thrust to said first surface of said second thrust-receiving portion;

a fourth flowrate, said fourth flowrate being the flowrate of fluid flowing to and providing thrust to said second surface of said second thrust-receiving portion;

actuation and retraction of said first gripper; and

actuation and retraction of said second gripper; and

wherein said logic component controls said valves of said tractors so as to actuate and retract one or more of said first grippers simultaneously, and also to actuate and retract one or more of said second grippers simultaneously.

16. Apparatus according to claim 15, wherein each of said tractors includes sensors on said tractor body, said sensors comprising one or more of:

position sensors sensing the positions of said thrust-receiving portions with respect to said grippers;

pressure sensors sensing the pressures of said first, second, third, and fourth flowrates; and

one of rotary accelerometers or potentiometers sensing the output of said motors;

wherein said sensors are configured to transmit electronic signals to said logic component.

17. A long reach drilling assembly for drilling a bore in an underground formation, the assembly including an elongated conduit extending from the surface through the bore;

a drill bit mounted at a forward end of the conduit for drilling the bore through the formation;

a 3-D steering tool secured to the conduit for making directional adjustments at the drill for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the conduit, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust to pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool; and

in which the 3-D steering tool comprises an integrated telemetry section, rotary section and flex section;

in which the flex section includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the rotary section is coupled to the actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments.

18. Apparatus according to claim 17 in which the deflection actuator comprises an elongated deflection housing surrounding the drive shaft, and an elongated hydraulically operated piston in the deflection housing for applying a bending force distributed lengthwise along the drive shaft for flexing the drive shaft to change inclination angle at the drill bit.

19. Apparatus according to claim 18 in which the rotator actuator is coupled to the deflection housing and includes a linear piston movable in proportion to a desired change in azimuth angle and a helical gear arrangement on the deflection housing coupled to the linear piston and rotatable in response to piston travel to rotate the deflection housing to change azimuth angle at the drill bit.

20. Apparatus according to claim 17 in which the hydraulically powered bending force is applied to the deflection piston by drilling mud taken from an annulus between the conduit and the borehole.

21. Apparatus according to claim 17 in which the deflection actuator applies the bending force to the drive shaft while the rotator actuator applies the rotational force to the drive shaft for making simultaneous adjustments in inclination angle and azimuth angle.

22. Apparatus according to claim 17 in which the feedback loop comprises a closed loop controller including a comparator for receiving the measured and desired inclination angle and azimuth angle command signals for producing inclination and azimuth error signals for making the steering adjustments.

23. Apparatus according to claim 17 in which the telemetry section comprises an onboard mud pulse telemetry section for receiving desired inclination and azimuth angle signals from the surface and utilizing mud pulse controls for operating the deflection actuator and rotator actuator from drilling mud taken from an annulus between the conduit and the borehole.

24. Apparatus according to claim 23 which the mud pulse telemetry section provides open loop control to the deflection actuator and the rotator actuator, and in which electrical controls provide closed loop control to the actuators.

25. A long reach drilling assembly for moving within a borehole, comprising:

an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course;

the steering tool including a rotary section and a flex section;

in which the flex section includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the rotary section is coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments;

a tractor body sized and shaped to move within the borehole;

a valve on said tractor body, said valve positioned along a flowpath between a source of fluid and a thrust-receiving portion of said body, said valve comprising;

a fluid port; and

a flow restrictor having a first position in which said restrictor completely blocks fluid flow through said fluid port, a range of second positions in which said restrictor permits a first level of fluid flow through said fluid port, a third position in which said restrictor permits a second level of fluid flow through said fluid port, said second level of fluid flow being greater than said first level of fluid flow;

a motor on said tractor body; and

a coupler connecting said motor and said flow restrictor, such that movement of said motor causes said restrictor to move between said first position, said range of second positions, and said third position, said restrictor being movable by said motor such that the net thrust received by said thrust receiving portion can be altered by 100 pounds within 0.5 seconds.

26. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the rotary drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard steering control section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course;

the steering tool having a rotary section and a flex section;

in which the flex section includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the rotary section is coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments;

a drilling tractor secured to the rotary drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portions relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore; and

a measurement-while-drilling device for providing drill bit positional information for the steering tool control section, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the measurement-while-drilling device, the 3-D steering tool and the drilling tractor.

27. Apparatus according to claim 26 in which the control section for the 3-D steering tool comprises mud pulse telemetry, and in which the propulsion assembly for the tractor comprises mud pulse telemetry for regulating pressure and/or flow of fluid within the tractor.

28. Apparatus according to claim 27 in which the control section for the 3-D steering tool comprises an integral electrical wire telemetry system, and in which the signals to the onboard controller for the tractor are delivered via an integral wire electrical telemetry system.

29. Apparatus according to claim 27 in which the rotary drill pipe includes a weight-on-bit sensor for use in controlling force applied to the drill bit by the tractor.

30. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe made from a composite material which includes a structural component comprised of a non-metallic material, the composite drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course;

the steering tool having a flex section which includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the steering tool includes a deflection actuator which includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, and in which rotational torque for driving the drill bit is delivered by the composite drill pipe and internal structural components of the 3-D steering tool and the drilling tractor.

31. Apparatus according to claim 30 in which hardwire electrical power and communication lines are integrated into the composite drill pipe for use in communicating control information to and from the 3-D steering tool and the tractor.

32. Apparatus according to claim 31 in which the telemetry section for the 3-D steering tool comprises an electrical wire telemetry system, and in which the signals to the onboard controller for the tractor are delivered via an integral electrical wire telemetry system.

33. Apparatus according to claim 30 in which the drill pipe includes a measurement-while-drilling tool for providing drill bit positional information to the controls for the steering tool.

34. Apparatus according to claim 30 in which the composite rotary drill pipe is in multiple sections with wet stab connectors for mechanically and electrically connecting the sections together.

35. Apparatus according to claim 30 in which the composite rotary drill pipe comprises layers of polymeric filament material impregnated with a resinous matrix.

36. A long reach drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe assembled in sections and extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle signals together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course via the telemetry section signals transmitted by integral electrical wire connections contained in the assembled sections of conduit;

in which the steering tool includes a flex section having an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the steering tool includes a rotary section coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore via signals transmitted by integral wire connections in the assembled sections of conduit, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool.

37. Apparatus according to claim 36 in which the drill pipe carries a measurement-while-drilling tool for providing drill bit positional information to the controls for the steering tool.

38. Apparatus according to claim 36 in which the sections of conduit are mechanically and electrically connected together by tool joints with wet stab connectors.

39. A long reach drilling assembly for drilling a bore in an underground formation, the assembly including an elongated conduit extending from the surface through the bore;

a drill bit mounted at a forward end of the conduit for drilling the bore through the formation in the absence of a downhole motor;

a 3-D steering tool secured to the conduit for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive the inclination angle and steering angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course;

in which the steering tool includes a flex section having an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the steering tool includes a rotary section coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments;

a drilling tractor secured to the conduit, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore;

a measurement-while-drilling device for providing drill bit positional information for the steering tool telemetry section; and

a weight-on-bit sensor for measuring thrust-of-tractor for use in the tractor controller, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool.

40. A long reach drilling assembly for drilling a bore in an underground formation, the assembly including an elongated conduit extending through the bore;

a drill bit mounted at a forward end of the conduit for drilling the bore through the formation in the absence of a downhole motor;

a 3-D steering tool carried on the conduit for making positional changes in three dimensions to steer the drill bit along a desired three-dimensional course, the 3-D steering tool including an onboard closed-loop feedback steering controller for receiving input positional commands and position-related feedback signals for turning the steering tool in response to changes in position-related commands;

the 3-D steering tool comprising a rotary section and a flex section;

in which the flex section includes an elongated drive shaft coupled to the drill bit and adapted to be rotatably driven for rotating the drill bit, the drive shaft being bendable laterally to define a deflection angle thereof, and a deflection actuator coupled to the drive shaft, the deflection actuator comprising a deflection housing surrounding the drive shaft and having a longitudinal axis and an elongated deflection piston movable in the deflection housing for applying a lateral bending force to the drive shaft for bending a wall section of the drive shaft away from the axis of the deflection housing while opposite end sections of the drive shaft are constrained by the housing for making changes in the deflection angle of the drive shaft which is transmitted to the drill bit as an inclination angle steering adjustment;

in which the rotary section is coupled to the deflection actuator and includes a rotator actuator for transmitting a rotational force to the deflection actuator to rotate the deflection piston to thereby change the rotational angle at which the lateral bending force is applied to the drive shaft which is transmitted to the drill bit as an azimuth angle steering adjustment; and

in which the telemetry section includes sensors for measuring the inclination angles and the azimuth angles of the steering tool while drilling, input signals proportional to the desired inclination angle and azimuth angle of the steering tool, and a feedback loop for processing measured and desired inclination angle and azimuth angle command signals for controlling operation of the deflection actuator for making inclination angle steering adjustments and for controlling operation of the rotary actuator for making azimuth angle steering adjustments;

a measurement-while-drilling device for locating drill bit position and orientation in the bore to produce feedback signals sent to the steering tool controller; and

a drilling tractor carried on the conduit for selectively applying force to the drill bit when needed to move the drill bit faster in the direction controlled by the steering tool.

41. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor;

in which the drilling tractor comprises;

a tractor body having a plurality of thrust receiving portions;

at least one valve on said tractor body positioned along at least one of a plurality of fluid flow paths between a source of fluid and said thrust receiving portions; and

a plurality of grippers, each of said plurality of grippers being longitudinally movably engaged with said body, each of said plurality of grippers having an actuated position in which said gripper limits movement of said gripper relative to an inner surface of said borehole and a retracted position in which said gripper permits substantially free relative movement of said gripper relative to said inner surface, said plurality of grippers, said plurality of thrust receiving portions and said valves being configured such said tractor can propel itself at a sustained rate of less than 50 feet per hour and at a sustained rate of greater than 100 feet per hour.

42. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor;

in which the drilling tractor comprises;

a tractor body having a thrust-receiving portion having a rear surface and a front surface;

a spool valve comprising;

a valve body having a spool passage defining a spool axis, said valve body having fluid ports which communicate with said spool passage; and

an elongated spool received within said spool passage and movable along said spool axis to control flowrates along fluid flow paths through said fluid ports and said spool passage, said spool having a first position range in which said valve permits fluid flow from a fluid source to said rear surface of said thrust-receiving portion and blocks fluid flow to said front surface, the flowrate of said fluid flow to said rear surface varying depending upon the position of said spool within said first position range, said fluid flow to said rear surface delivering downhole thrust to said body, the magnitude of said downhole thrust depending on the flowrate of said fluid flow to said rear surface, said spool having a second position range in which said valve permits fluid flow from said fluid source to said front surface of said thrust-receiving portion and blocks fluid flow to said rear surface, the flowrate of said fluid flow to said front surface varying depending upon the position of said spool within said second position range, said fluid flow to said front surface delivering uphole thrust to said body, the magnitude of said uphole thrust depending on the flowrate of said fluid flow to said front surface;

a motor on said tractor body;

a coupler connecting said motor and said spool so that operation of said motor causes said spool to move along said spool axis; and

a gripper longitudinally movably engaged with said tractor body, said gripper having an actuated position in which said gripper limits movement of said gripper relative to an inner surface of said borehole and a retracted position in which said gripper permits substantially free relative movement of said gripper relative to said inner surface;

wherein said motor is operable to move said spool along said spool axis sufficiently fast to alter the net thrust received by said thrust-receiving portion by 100 pounds within 2 seconds.

43. Apparatus according to claim 42, further comprising:

one or more sensors on said tractor body, configured to generate electrical feedback signals which describe one or more of fluid pressure in said tractor, the position of said tractor body with respect to said gripper, longitudinal load exerted on said tractor body by equipment external to said tractor or by inner walls of said borehole, and the rotational position of an output shaft of said motor, said output shaft controlling the position of said spool along said spool axis; and

an electronic logic component on said tractor body, configured to receive and process said electrical feedback signals, said logic component configured to transmit electrical command signals to said motor;

wherein said motor is configured to be controlled by said electrical command signals, said command signals controlling the position of said spool.

44. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor;

in which the drilling tractor comprises;

a body;

a valve on said body, said valve being positioned along a fluid flow path from a source of a first fluid to a thrust-receiving portion of said body, said valve being movable generally along a valve axis, said valve having a first position in which said valve completely blocks fluid flow along said flow path and a second position in which said valve permits fluid flow along said flow path;

a motor on said body;

a coupler connecting said motor and said valve so that operation of said motor causes said valve to move along said valve axis; and

a pressure compensation piston exposed on a first side to said first fluid and on a second side to a second fluid, said first and second fluids being fluidly separate, said piston configured to move in response to pressure forces from said first and second fluids so as to effectively equalize the pressure of said first and second fluids;

wherein said valve is exposed to said first fluid, said motor being exposed to said second fluid.

45. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor;

in which the drilling tractor comprises;

an elongated body configured to pull equipment within said borehole,

said equipment exerting a longitudinal load on said body;

a gripper longitudinally movably engaged with said body, said gripper having an actuated position in which said gripper limits movement between said gripper and an inner surface of said borehole, and a retracted position in which said gripper permits substantially free relative movement between said gripper and said inner surface; and

a propulsion system on said body for propelling said body through said borehole while said gripper is in said actuated position;

wherein said body is sufficiently flexible such that said tractor can turn up to 80°

per 100 feet of travel, while said longitudinal load is at least 50-30,000 pounds.

46. A long reach rotary drilling assembly for drilling a bore in an underground formation, the assembly including an elongated rotary drill pipe extending from the surface through the bore;

a drill bit mounted at a forward end of the drill pipe for drilling the bore through the formation;

a 3-D steering tool secured to the drill pipe for making inclination angle adjustments and azimuth angle adjustments at the drill bit during steering, including an onboard telemetry section to receive inclination angle and azimuth angle commands together with actual inclination angle and azimuth angle feedback signals during steering for use in controlling steering of the drill bit along a desired course; and

a drilling tractor secured to the drill pipe, the tractor comprising a body, a gripper secured to the body, including a gripper portion having a first position which limits movement of the gripper portion relative to the inner surface of the bore and having a second position in which the gripper portion permits relative movement between the gripper portion and the inner surface of the bore, a propulsion assembly for selectively continuously pulling and thrusting the body with respect to the gripper portion in the first position, and an onboard controller for controlling thrust or pull or speed of the tractor in the bore, the tractor applying force to the drill bit for drilling the bore along the desired course the direction of which is controlled by the steering tool, rotary torque for driving the drill bit transmitted from the surface through the drill pipe and structural components of the 3-D steering tool and the drilling tractor;

including a set of two or more connected tractors for moving within the borehole, comprising a logic component and said tractors, each of said tractors comprising;

grippers simultaneously, and also to actuate and retract one or more of said second grippers simultaneously.

47. Apparatus according to claim 46, wherein said valves are controlled by motors, said logic component configured to transmit electronic command signals to said motors, said motors being controlled by said electronic command signals.

48. Apparatus according to claim 46, wherein said logic component resides within one of said tractors.