Drilling system with an acoustic measurement-while-driving system for determining parameters of interest and controlling the drilling direction

• US 6,088,294 A
• Filed: 01/24/1997
• Issued: 07/11/2000
• Est. Priority Date: 01/12/1995
• Status: Expired due to Term

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Seaton, Paul J. G., Balogh, William Thomas, Dubinsky, Vladimir, Leggett, James V. III, Brooks, Andrew G., Harrell, John W., Herbert, Roger P.
• Primary Examiner(s): Oda, Christine K.
• Assistant Examiner(s): Taylor, Victor J.
• Application Number:
  US08/789,230
• Time in Patent Office: 1,264 Days
• Field of Search: 181/104, 181/105, 367/25, 367/34, 367/31, 367/33, 175/40, 175/26, 73/152.03, 166/250.01, 364/421
• US Class Current: 367/25
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
• CPC Class Codes: E21B 44/005 Below-ground automatic control systems
• CPC Class Codes: G01V 1/48 Processing data
• CPC Class Codes: G01V 1/52 Structural details
• CPC Class Codes: G01V 1/523 Damping devices

Abstract

The present invention provides a system for drilling boreholes having a downhole subassembly which contains an acoustic measurement-while-drilling system. The acoustic system contains an acoustic transmitter and receiver for determining the acoustic velocity through the formations surrounding the borehole ad an acoustic transmitter and a set of receivers for determining the bed boundaries surrounding the borehole formation utilizing the acoustic velocities measured by the system. The downhole subassembly also contains a computing system which performs computations downhole and transmits certain answers uphole during the drilling operations. The bed boundary information is utilized to drill the wellbore along a desired wellbore path. The downhole computing system correlates the acoustic sensor measurements with other measurement-while-drilling measurements and transmits selected correlated information uphole. The downhole computing system contains predetermined well profile which is updated based on the bed boundary information. The system may be adapted to correct or update seismic data and offset well data based on acoustic sensor system measurements.

Claims

1. A downhole tool for use in drilling of a wellbore, comprising:

(a) a transmitter transmitting acoustic signals at a first frequency and a second frequency into a formation surrounding the borehole during drilling of the wellbore;

(b) at least one receiver detecting signals transmitted by the transmitter; and

(c) a processor carried by the tool, said processor determining;

(i) downhole acoustic velocity of the subsurface formation from the at least one receiver signals at the first frequency, and

(ii) distance between the tool and a subsurface reflection point from the determined acoustic velocity and the at least one receiver signal at the second frequency during drilling of the wellbore.

2. The downhole tool according to claim 1, wherein the at least one receiver includes a far receiver which is utilized for determining said acoustic velocity.

3. The downhole tool according to claim 2, wherein the far receiver includes a plurality of axially spaced acoustic sensors, each such sensor detecting acoustic signals reflected by the reflection point.

4. The downhole tool according to claim 3, wherein at least one acoustic sensor in the plurality of sensors is utilized for determining the travel time.

5. The downhole tool according to claim 3, wherein each axially spaced acoustic sensor contains a plurality of receiver elements circumferentially disposed around the downhole tool.

6. The downhole tool according to claim 2, wherein the at least one receiver further includes a near receiver which is utilized for determining the travel time.

7. The downhole tool according to claim 6, wherein the near receiver includes at least two acoustic sensors symmetrically disposed about the transmitter in the downhole tool for reducing the effect on the near receiver of signals other than the acoustic signals reflected from the reflection point.

8. The downhole tool according to claim 6 further comprising an isolator between the transmitter and the near receiver for reducing the effect of acoustic waves traveling in the downhole tool on the near receiver.

9. The downhole tool according to claim 1, wherein the near receiver includes a plurality of axially spaced acoustic sensors along the downhole tool.

10. The downhole tool according to claim 1, wherein the receiver comprises:

(I) a far receiver having least one acoustic sensors along the downhole tool; and

(II) a near receiver containing a plurality of axially spaced acoustic sensors along the downhole tool.

11. The downhole tool according to claim 10, wherein the distance between the transmitter and a reference point of the far receiver is greater than the distance between the transmitter a reference point the near receiver.

12. A downhole tool for use in drilling of a wellbore, comprising:

(a) a first acoustic sensor arrangement disposed in the downhole tool for determining acoustic velocity of a formation around the wellbore during drilling of the wellbore based upon signals transmitted by a transmitter in the first sensor arrangement at a first frequency; and

(b) a second acoustic sensor arrangement disposed in the downhole tool for measuring acoustic travel time between the downhole tool and a subsurface reflection point based on signals transmitted by a transmitter in the second sensor arrangement at a second frequency.

13. The downhole tool according to claim 12, wherein the first acoustic sensor arrangement further comprises a receiver and the second acoustic sensor arrangement further comprises a plurality of receivers.

14. The downhole tool according to claim 13, wherein the transmitter in the first and second acoustic sensor arrangements is a common transmitter.

15. The downhole tool according to claim 12, wherein the distance between the transmitter and the receiver in the first acoustic sensor arrangement is substantially less than the distance between the transmitter and receiver in the second acoustic sensor arrangement.

16. The downhole tool according to claim 12, wherein the second acoustic sensor arrangement includes two acoustic sensors symmetrically disposed about the transmitter of the second acoustic arrangement.

17. The downhole tool according to claim 16 further comprising an acoustic isolator disposed between the transmitter of the second acoustic arrangement and each of the two symmetrically disposed acoustic sensors for reducing the effect of body waves.

18. The downhole tool according to claim 16, wherein one of the two acoustic sensors acts as the receiver of the first acoustic arrangement.

19. The downhole tool according to claim 12 further having a device selected from a group consisting of a (i) device for determining porosity of the formation around the downhole tool during drilling of the wellbore, (ii) device for determining density of the formation around the downhole tool during drilling of the wellbore, and (iii) device for determining the resistivity of the formation, a device for determining the inclination of the tool in the wellbore and a nuclear device.

20. The downhole tool according to claim 12, wherein the receiver in the first and second acoustic sensor arrangements is a common array having a plurality of axially spaced acoustic sensors.

21. The downhole tool according to claim 20, wherein the receiver in the first and second acoustic sensor arrangements is a common array of a plurality of axially spaced acoustic sensors.

22. The downhole tool according to claim 12, wherein the transmitters in the first and second acoustic sensor arrangements are disposed on either side of the array, with the distance between the transmitter of the first acoustic sensor arrangement and a center of the array being less than the distance between the transmitter of the second acoustic sensor arrangement and a selected sensor in the array.

23. The downhole tool according to claim 12, further comprising processor for receiving signals from the first and second acoustic sensor arrangements and in response thereto determining the location of a formation boundary relative to the downhole tool.

24. The downhole tool according to claim 23, wherein the processor first determines the acoustic velocities and then utilizess such computed velocities to determine the bed boundaries.

25. The downhole tool according to claim 23 wherein the processor contains a computer and an associated memory.

26. The downhole tool according to claim 25, wherein the processor determines a three dimensional map of the bed boundaries of the formation around the downhole tool.

27. The downhole tool according to claim 24, wherein the processor includes a predetermined profile of the location of the wellbore in the formation.

28. The downhole tool according to claim 27, wherein the processor updates the wellbore profile based on the bed boundary information.

31. The drilling assembly according to claim 24 further comprising a drilling motor disposed between the drill bit and the acoustic device for rotating the drill bit when a pressurized fluid is passed through the drilling motor.

32. The drilling assembly according to claim 31 wherein the steering device is disposed between the drill bit and the mud motor.

29. A drilling assembly for use in drilling of a wellbore, comprising:

(a) a drill bit at an end of the drilling assembly for drilling the wellbore;

(b) an acoustic device having a transmitter for transmitting acoustic signals at a first frequency and a second frequency in the wellbore during drilling of the wellbore and a receiver for detecting signals transmitted by the transmitter;

(c) a processing system associated with the drilling assembly for processing signals from the receiver at the first frequency for determining an acoustic velocity of a formation surrounding the wellbore and at the second frequency for determining a travel time from the drilling assembly to a subsurface reflection point; and

(d) a steering device disposed in the drilling assembly for altering direction of drilling the wellbore by the drill bit.

30. The drilling assembly according to claim 29, wherein the steering devise includes a plurality of independently controllable members, each said member adapted to extend outwardly from the drilling assembly.

33. The bottomhole assembly according to claim 29 further comprising a resistivity device for determining the presence of hydrocarbon bearing formations during drilling of the wellbore.

34. The bottomhole assembly according to claim 29 further comprising a nuclear device for determining nuclear porosity of the formation around the drilling assembly during drilling of the wellbore.

35. The drilling assembly according to claim 34 further comprising a device for determining density of the formation around the drilling tool during drilling of the wellbore.

36. The drilling assembly according to claim 29, wherein the processing system:

(i) includes a well profile;

(ii) determines the position of the drilling assembly relative to the well profile; and

(iii) generates a signal representative of a difference between the well profile and the drilling assembly position.

37. The drilling assembly according to claim 36, wherein the processing system causes the steering device to alter the drilling direction in response to the generated signal so as to maintain drilling of the wellbore along the wellbore profile.

38. The drilling assembly according to claim 29, wherein the processing system determines a three dimensional map of the bed boundaries of the formation around the downhole tool.

39. The drilling assembly according to claim 29 further having a wellbore profile stored in a memory in the drilling assembly.

40. The drilling assembly according to claim 36, wherein the processing system determines the location of the drilling assembly in relation to a boundary of the formation surrounding the drilling assembly.

41. The drilling assembly according to claim 40, wherein the processing system updates the wellbore profile based on the bed boundary information.

42. The drilling assembly according to claim 29, wherein the processing system determines a three dimensional map of the bed boundaries of the formation around the downhole tool.

43. The drilling assembly according to claim 29 further comprising a sensor disposed in the drilling assembly near the drill bit for determining characteristics of acoustic signals transmitted by the drill bit during drilling of the wellbore.

44. The drilling assembly according to claim 43, wherein the processing system receives signals from at least one receiver in the acoustic device that are responsive to acoustic signals transmitted by the drill bit during drilling of the wellbore and processes such received signals based on the characteristics of the acoustic signals transmitted by the drill bit to (a) determine the position of the drilling assembly relative to a subsurface formation boundary, (b) update a wellbore profile provided to the drilling assembly or (c) obtain a seismograph of the subsurface formations surrounding the drilling assembly.

45. A downhole tool for use in drilling of a wellbore, comprising:

(a) an acoustic transmitter disposed in the downhole tool for transmitting acoustic signals into a formation surrounding the wellbore during drilling of the wellbore;

(b) a pair of acoustic receivers symmetrically disposed about the transmitter, said receivers detecting at least acoustic signals reflected by a subsurface reflection point in the formation in response to the transmitted signals, and

(c) a processor using said symmetric disposition to reduce the effect of acoustic signals other than the acoustic signals reflected by the subsurface reflection point in the formation.

46. The downhole tool according to claim 45 wherein the processor incorporates the subtraction of the acoustic signal detected by one of the pair of acoustic receivers from the acoustic signal detected by the other of the pair of acoustic receivers.

47. The downhole tool according to claim 45, wherein the processor is adapted to cause the transmitter to operate at a frequency selected from a range of frequencies.

48. The downhole tool according to claim 45 further comprising an acoustic isolator disposed between the transmitter and each of the acoustic receivers for reducing the effect of acoustic signals transmitted by the transmitter that travel through the downhole tool.

49. A downhole tool for use in drilling of a wellbore in a formation, comprising:

(a) a first acoustic sensor arrangement including at least one transmitter and at least one acoustic receiver for providing signals indicative of acoustic velocity of a formation surrounding the wellbore;

(b) a second acoustic sensor arrangement including a transmitter and a pair acoustic receivers substantially symmetrically disposed about the transmitter for providing a pair of signals indicative of a first position of the downhole tool relative to a subsurface bed boundary in the formation; and

(c) a processor for

(i) determining an acoustic velocity of the formation from the first acoustic sensor arrangement, and

(ii) determining the first position of the downhole tool relative to the subsurface bed boundary from the determined acoustic velocity and the pair of signals from the second acoustic sensor arrangements.

50. The downhole tool according to claim 49 further comprising a third acoustic sensor arrangement having a transmitter and a pair of acoustic receivers for providing a pair of signals indicative of a second position of the downhole tool relative to the subsurface bed boundary.

51. The downhole tool according to claim 50, wherein the processor utilizes the pair of signals from the third acoustic sensor arrangements to determine the second position of the downhole tool relative to the subsurface bed boundary.

52. The downhole tool according to claim 51, wherein the processor determines dip of the subsurface formation bed boundary from the first and second positions of the downhole tool.

53. The downhole tool of claim 49 wherein the first sensor arrangement and the second sensor arrangement have at least one receiver in common.

54. The downhole tool of claim 49 wherein the first sensor arrangement and the second sensor arrangement have at least one transmitter in common.

55. The downhole tool of claim 49 wherein the wherein the processor incorporates the subtraction of the signal provided by one of the pair of acoustic sensors from the signal provided by the other of the pair of acoustic sensors.

56. The downhole tool of claim 49, the second sensor arrangement further comprising an acoustic isolator disposed between the transmitter and each of the acoustic receivers for reducing the effect of acoustic signals transmitted by the transmitter that travel through the downhole tool.

57. The downhole tool of claim 49 wherein the at wherein the at least one acoustic receiver in the first sensor arrangement includes a far receiver that is utilized for determining said acoustic velocity.

58. The downhole tool of claim 57 wherein the far receiver includes a plurality of spaced apart acoustic sensors, each such sensor detecting transmitted acoustic signals traveling parallel to the wellbore.

59. The downhole tool of claim 58, wherein each acoustic sensor contains a plurality of receiver elements circumferentially disposed around the downhole tool.

60. The downhole tool according to claim 57, wherein the distance between a transmitter and the far receiver in the first acoustic sensor arrangement is substantially less than the distance between the transmitter and an acoustic receiver in the second acoustic sensor arrangement.

61. The downhole tool according to claim 49 further having a device selected from a group consisting of a (i) device for determining porosity of the formation around the downhole tool during drilling of the wellbore, (ii) device for determining density of the formation around the downhole tool during drilling of the wellbore, and (iii) device for determining the resistivity of the formation, a device for determining the inclination of the tool in the wellbore and a nuclear device.

62. The downhole tool according to claim 49, wherein the processor further determines a three dimensional map of the bed boundaries of the formation around the downhole tool.

63. A downhole tool for use in drilling of a wellbore in a formation, comprising:

(a) an acoustic sensor arrangement including a transmitter and a pair acoustic receivers substantially symmetrically disposed about the transmitter for providing signals indicative of a first position of the downhole tool relative to a subsurface bed boundary in the formation; and

(c) a processor for determining the first position of the downhole tool relative to the subsurface bed boundary from an acoustic velocity of the formation and signals from the acoustic sensor arrangement.

64. A drilling assembly for use in drilling of a wellbore, comprising:

(a) a drill bit at an end of the drilling assembly for drilling the wellbore;

(b) a first acoustic sensor arrangement including at least one transmitter and at least one acoustic receiver for providing signals indicative of acoustic velocity of a formation surrounding the wellbore;

(c) a second acoustic sensor arrangement including a transmitter and a pair acoustic receivers substantially symmetrically disposed about the transmitter for providing signals indicative of a first position of the downhole tool relative to a subsurface bed boundary; and

(d) a processor for;

(i) determining an acoustic velocity of the formation from the first acoustic sensor arrangement, and

(ii) determining the first position of the downhole tool relative to the subsurface bed boundary from the determined acoustic velocity and signals from the second acoustic sensor arrangements, and

(iii) controlling a steering device disposed in the drilling assembly to alter the direction of drilling of the wellbore by the drill bit in response to said determined first position.

65. A method of drilling a borehole in a formation utilizing a downhole tool having a first and second acoustic sensor arrangements during drilling of the borehole, comprising:

(a) conveying the downhole tool in the borehole;

(b) using the first sensor arrangement to provide signals indicative of the acoustic velocity of the formation;

(c) using a transmitter in the second sensor arrangement to transmit acoustic signals into the formation;

(d) detecting acoustic signals reflected by a subsurface bed boundary by a pair of acoustic receivers disposed substantially symmetrically about the transmitter in the second sensor arrangement;

(e) using the processor to determine the acoustic velocity of the formation from the signals provided by the first sensor arrangement; and

(f) using the processor to determine a position of the subsurface bed boundary in the formation from the determined acoustic velocity and the signals detected by the pair of acoustic receivers.