MICROHYDRAULIC FRACTURING WITH DOWNHOLE ACOUSTIC MEASUREMENT

• US 20100157737A1
• Filed: 04/28/2009
• Published: 06/24/2010
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: LATIFZAI, AHMAD, WANG, CANYUN, PRIOUL, ROMAIN CHARLES ANDRE, MILLER, DOUGLAS E., MACKAY, BRUCE A., HAUSOT, ANDREAS, FARAHANI, ALIREZA, MULLINS, OLIVER C.
• Granted Patent: US 9,477,002 B2
• Time in Patent Office: Days
• US Class Current: 367/117
• CPC Class Codes: E21B 33/124 Units with longitudinally-spaced plugs for isolating the intermediate space
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: E21B 47/107 using acoustic means
• CPC Class Codes: G01V 1/46 Data acquisition

Abstract

Methods and related systems are described for measuring acoustic signals in a borehole during a fracturing operation. The system includes a downhole toolstring designed and adapted for deployment in a borehole formed within a subterranean rock formation. A downhole rock fracturing tool opens and propagates a fracture in the subterranean rock formation. Dipole and/or quadrupole acoustic sources transmit acoustic energy into the subterranean rock formation. A receiver array measures acoustic energy traveling through the subterranean rock formation before, during and after the fracture induction. Geophones mounted on extendable arms can be used to measure shear wave acoustic energy travelling in the rock formation. The toolstring can be constructed such that the sources and receivers straddle the fracture zone during the fracturing. Alternatively, the sources or the receivers can co-located axially with the fracture zone, or the toolstring can be repositioned following fracturing such that the fracture zone is between the acoustic sources and receivers.

Claims

1. A system for measuring acoustic signals in a borehole during a fracturing operation:

a downhole toolstring designed and adapted for deployment in a borehole formed within a subterranean rock formation;

a downhole rock fracturing tool forming part of the toolstring, designed and adapted to open and propagate a fracture in the subterranean rock formation;

one or more acoustic sources mounted to the toolstring, designed and adapted to transmit acoustic energy into the subterranean rock formation; and

one or more sensors mounted to the toolstring, designed and adapted to measure part of the acoustic energy traveling through the subterranean rock formation.

2. A system according to claim 1 wherein the downhole rock fracturing tool comprises a downhole pumping system mounted to the toolstring and adapted to pump fluid into an annular region defined by at least the toolstring and a wall of the borehole

3. A system according to claim 1 wherein the one or more acoustic sources include two multi-pole sources each capable of generating a multi-pole acoustic signal.

4. A system according to claim 3 wherein the two multi-pole sources are dipole sources and are mounted such that they are oriented orthogonally with respect to each other.

5. A system according to claim 3 wherein the two multi-pole sources are quadrupole acoustic sources.

6. A system according to claim 1 wherein the one or more sensors includes one or more geophones mounted to the toolstring, designed and adapted to measure part of the acoustic energy traveling through the subterranean rock formation.

7. A system according to claim 6 wherein each geophone is a 3-axis geophone and is mounted on an extendable member such that the geophone can be in direct communication with the borehole wall and shear components of the acoustic energy traveling in the rock formation can be measured.

8. A system according to claim 1 wherein the one or more sensors include acoustic sensors that make up an acoustic receiver array including a plurality of receiver stations spaced apart along the axis of the downhole toolstring, and each receiver station including a plurality of azimuthally distributed acoustic sensors at substantially the same axial position.

9. A system according to claim 1 wherein the rock fracturing tool and the one or more acoustic sources and sensors are arranged along the axis of the toolstring such that axial positions of the one or more sources are on one side of the location of the rock to be fractured and the axial positions of the one or more receivers are on the other side.

10. A system according to claim 1 wherein the one or more sources and the rock fracturing tool are arranged on the toolstring such that the axial positions of the one or more sources and the axial position of the rock to be fractured is substantially the same.

11. A system according to claim 1 wherein the one or more sources and the rock fracturing tool are arranged on the toolstring such that the axial positions of the one or more receivers and the axial position of the rock to be fractured is substantially the same.

12. A system according to claim 1 wherein the fracturing tool, sources and receivers are arranged on the toolstring such that following an induced fracturing of rock, the toolstring can be repositioned so that the induced fracture is between the source and receiver.

16. A system according to claim 1 further comprising a processor adapted to evaluate one or more properties of the rock formation, and the evaluation is based at least in part on the acoustic energy traveling through the rock formation as measured by the one or more sensors.

21. A system according to claim 1 wherein the rock fracturing tool comprises a first and second member designed and positioned to seal the region between the toolstring and a wall of the borehole such that an annular region is defined by the tool housing, the borehole wall, and the first and second members.

25. A system according to claim 1 further comprising an orientation tool for making measurements such that measurements from the one or more sensors can be oriented.

13. A system according to claim 13 wherein the fracturing tool includes a pumping system adapted to inject proppant material into the induced fracture such that closure of the induced fracture is prevented or delayed.

14. A system according to claim 14 wherein the proppant material includes one or more materials selected from the group consisting of calcined calcium carbonate, polyester beads, crystalline sodium chloride, and magnesium oxide.

15. A system according to claim 14 wherein the fracture is propagated with a resinous material that forms a solid mass after a predetermined time.

17. A system according to claim 17 wherein the one or more properties includes direction and speed of sonic propagation within the rock formation.

18. A system according to claim 17 wherein the one or more properties includes far field stress and/or fracture properties.

19. A system according to claim 17 wherein the one or more properties are for locations having a distance from the borehole wall of greater than the diameter of the borehole.

20. A system according to claim 17 wherein processor is programmed to combine data based on measurements of acoustic energy after an induced rock fracture with reference data based on measurements of acoustic energy prior to and/or during the induction of rock fracturing.

22. A system according to claim 22 wherein the first and second members are expandable packers attached to the tool and making contact with the borehole wall when deployed.

23. A system according to claim 23 wherein the one or more sensors are positioned on the toolstring so as to be in primary acoustic communication with locations other than the annular region.

24. A system according to claim 23 wherein the one or more receivers are positioned on the toolstring so as to be in primary acoustic communication with locations other than the annular region.

26. A method for measuring acoustic signals in a borehole during a fracturing operation, comprising:

positioning a downhole toolstring in a borehole formed within a subterranean rock formation;

inducing fracturing in rock formation using a rock fracturing tool forming part of the toolstring;

transmitting acoustic energy into the rock formation using one or more acoustic sources mounted to the toolstring; and

measuring acoustic energy traveling through the rock formation using one or more sensors mounted to the toolstring.

27. A method according to claim 27 wherein the one or more acoustic sources are multi-pole acoustic sources, and the acoustic energy transmitted includes multi-pole acoustic energy.

30. A method according to claim 27 wherein the one or more sensors include a plurality of acoustic sensors arranged on the toolstring so as to be capable of detecting multi-pole acoustic energy.

31. A method according to claim 27 wherein the one or more sensors include one or more geophones.

33. A method according to claim 27 wherein the rock fracturing tool and the one or more acoustic sources and sensors are arranged along the axis of the toolstring such that axial positions of the one or more sources are on one side of the location of the induced rock fracture and the axial positions of the one or more receivers are on the other side.

34. A method according to claim 27 wherein the one or more sources and the rock fracturing tool are arranged on the toolstring such that the that axial positions of the one or more sources and the axial position of the induced rock fracture is substantially the same.

35. A method according to claim 27 wherein the one or more sources and the rock fracturing tool are arranged on the toolstring such that the that axial positions of the one or more receivers and the axial position of the induced rock fracture is substantially the same.

36. A method according to claim 27 further comprising repositioning the toolstring after inducing the fracturing such that the induced fracture is between the source and receiver.

40. A method according to claim 27 further comprising evaluating one or more properties of the rock formation based at least in part on the measuring of acoustic energy.

45. A method according to claim 27 wherein the fracturing induction comprises sealing an annular region that is a volume bounded by a first sealing member, a second sealing member, the outer surface of the toolstring, and the borehole wall.

28. A method according to claim 28 wherein the one or more multi-pole acoustic sources include two orthogonally oriented dipole sources and the transmitted acoustic energy includes dipole acoustic energy.

29. A method according to claim 28 wherein the one or more multi-pole acoustic sources include one or more quadrupole acoustic sources and the transmitted acoustic energy includes quadrupole acoustic energy.

44. A method according to claim 29 wherein the transmitting comprises repeatedly generating alternating pulses from each of the two dipole sources with a predetermined delay between successive pulses.

32. A method according to claim 32 wherein each of the geophones is a 3-axis geophone mounted on a extendable member such that the geophone can be in direct communication with the borehole wall, and wherein the measuring includes measuring shear components of the acoustic energy traveling in the rock formation.

37. A method according to claim 37 further comprising injecting proppant material into the induced fracture such that closure of the induced fracture is prevented or delayed.

38. A method according to claim 38 wherein the proppant material includes one or more materials selected from the group consisting of calcined calcium carbonate, polyester beads, crystalline sodium chloride, and magnesium oxide.

39. A method according to claim 39 wherein the inducing fracturing includes propagating the fracture with a resinous material that forms a solid mass after a predetermined time.

41. A method according to claim 41 wherein the one or more properties includes direction and speed of sonic propagation within the rock formation.

42. A method according to claim 41 wherein the one or more properties includes far field stress and/or fracture properties.

43. A method according to claim 41 wherein the evaluating comprises combining data based on measurements of acoustic energy after the induced fracturing with reference data based on measurements of acoustic energy prior to and/or during the induced fracturing.

46. A method according to claim 46 wherein the fracturing further comprises pumping fluid into the annular region so as to significantly increase the fluid pressure in the annular region thereby inducing the fracture.

47. A method according to claim 46 wherein the one or more sensors are positioned on the toolstring so as to be in primary acoustic communication with locations other than the annular region.

48. A method according to claim 46 wherein the one or more receivers are positioned on the toolstring so as to be in primary acoustic communication with locations other than the annular region.