LIQUID CARBON DIOXIDE CLEANING OF WELLBORES AND NEAR-WELLBORE AREAS USING HIGH PRECISION STIMULATION

• US 20080142224A1
• Filed: 12/18/2006
• Published: 06/19/2008
• Est. Priority Date: 12/18/2006
• Status: Active Grant

• Current Assignee: Conocophillips Company (ConocoPhillips)
• Original Assignee: Conocophillips Company (ConocoPhillips)
• Inventors: WILSON, Dennis Ray
• Granted Patent: US 7,677,317 B2
• Time in Patent Office: Days
• US Class Current: 166/308.2
• CPC Class Codes: E21B 37/06 using chemical means for preventing or limiting , e.g. eliminating, the deposition of paraffins or like substances
• CPC Class Codes: E21B 43/114 Perforators using direct fluid action on the wall to be perforated, e.g. abrasive jets
• CPC Class Codes: E21B 43/267 reinforcing fractures by propping

Abstract

A method to clean a wellbore and the near wellbore area adjacent to the wellbore of a hydrocarbon bearing formation adjacent to the production zone of the wellbore is provided. A method to clean a casing inserted into a wellbore is also disclosed. A method for cleaning a wellbore of fracturing fluid, with or without proppant is also disclosed. Each of the methods includes the steps of injecting either liquid carbon dioxide or a treatment medium comprising liquid carbon dioxide into a wellbore through tubing such that the location at which the treatment medium is administered may be controlled. In some embodiments, pressure within the wellbore is regulated in order to either maintain the treatment medium in the liquid state, or allow at least a portion of the treatment medium to vaporize upon introduction into the wellbore. Once the treatment medium has at least partially vaporized it will loosen and/or entrain undesirable materials from within the wellbore or casing. The gaseous portion of the treatment medium is allowed to escape through the wellhead, carrying with it the undesirable materials.

Claims

1. A method for cleaning a wellbore and near wellbore areas in a formation comprising the steps of:

inserting a desired length of tubing into said wellbore;

introducing a treatment medium comprising liquid carbon dioxide through said tubing into one or more locations within said wellbore and into at least a portion of said formation adjacent to said wellbore; and

vaporizing at least a portion of said treatment medium after it is injected into said wellbore.

2. The method of claim 1, further comprising the steps of:

prior to introducing said treatment medium, closing said wellbore;

regulating pressure within said wellbore such that at least a portion of said treatment medium remains in a liquid state following injection into said wellbore; and

following injection of said treatment medium, releasing said pressure within said wellbore such that at least a portion of said treatment medium vaporizes.

3. The method of claim 2 further comprising the step of repeating said steps of closing said wellbore, and releasing said pressure at least once.

4. The method of claim 1, wherein said formation has a known pressure at which said formation fractures and said treatment medium is introduced into said wellbore such that said pressure within said formation remains below said pressure at which said formation fractures.

5. The method of claim 1, wherein said formation has a known pressure at which said formation fractures and wherein said treatment medium is introduced into said wellbore such that said pressure within said formation remains below 75% of said pressure at which said formation fractures.

6. The method of claim 1, wherein said formation has a known pressure at which said formation fractures and wherein said treatment medium is introduced into said wellbore such that said pressure within said formation remains below 50% of said pressure at which said formation fractures.

7. The method of claim 1, wherein said tubing is coiled tubing.

8. The method of claim 1 further comprising the step of impinging said wellbore and said near wellbore area with said treatment medium.

9. The method of claim 1 wherein at least a portion of said wellbore is drilled at an angle of greater than zero degrees from vertical, the additional step of impinging said treatment medium into said sections of said wellbore which are at an angle of greater than zero degrees from vertical.

10. The method of claim 1 further comprising the step of injecting said treatment medium at a rate of at least two barrels per minute.

11. The method of claim 1, wherein said wellbore is at least a partially open hole wellbore.

12. The method of claim 1, wherein said wellbore is an open hole completion.

13. The method of claim 1, wherein said formation is a hydrocarbon bearing formation.

14. The method of claim 1, wherein said formation is a gas bearing formation.

15. The method of claim 1, wherein said formation is an oil bearing formation.

16. The method of claim 1, wherein at least a portion of said treatment medium dissolves in water.

17. The method of claim 1, wherein said vaporized treatment medium removes undesirable materials and/or water from said wellbore and near wellbore areas.

18. The method of claim 1 further comprising the step of forming depressions in said formation near said wellbore.

19. The method of claim 1 wherein said treatment medium is injected at a pressure of at least approximately 1,000 psi.

20. The method of claim 1 wherein said treatment medium further comprises abrasives.

21. The method of claim 1, wherein said treatment medium further comprises alcohol, surfactant, corrosion inhibitor, acid, iron-control chemical, biocide, and/or abrasives.

22. The method of claim 1, wherein said treatment medium is in the following proportions by volume:

from about 84.5 to 100% liquid carbon dioxide;

from about 0 to 15% of an alcohol; and

from about 0 to 0.5% surfactant.

23. A method for cleaning deposits from a portion of casing in a wellbore in a formation, comprising the steps of:

inserting into said casing a known length of tubing such that said tubing terminates at a known location within said casing;

introducing, through said tubing, treatment medium comprised of liquid carbon dioxide to said known location;

impinging said casing with said treatment fluid;

removing at least some deposits from said portion of said casing;

regulating the pressure within the wellbore to partially vaporize said treatment medium such that the partially vaporized treatment medium entrains said deposits; and

allowing said partially vaporized treatment medium and entrained deposits to exit said casing.

25. The method of claim 23, wherein said treatment medium further comprises alcohol, surfactant, corrosion inhibitor, acid, iron-control chemical, biocide, and/or abrasives.

26. The method of claim 23, wherein said treatment medium further comprises abrasive, wherein said abrasive is mixed with said treatment medium at a ratio of at least about 0.25 pounds of said abrasive to one gallon of said treatment medium.

24. A method for cleaning deposits from the surface of one or more perforations in a casing in a wellbore in a formation, comprising the steps of:

inserting into said casing a known length of tubing such that said tubing terminates at a location within said casing which is adjacent at least one of said one or more perforations;

introducing, through said tubing, treatment medium comprised of liquid carbon dioxide to said known location;

impinging said surface of said one or more perforations with said treatment fluid;

removing at least some deposits from said surface of said one or more perforations;

regulating the pressure within the wellbore to partially vaporize said treatment medium such that the partially vaporized treatment medium entrains said deposits; and

opening said wellbore to allow said partially vaporized treatment medium and entrained deposits to exit said casing.

27. A method for fracturing a fluid bearing formation having a wellbore comprising the steps of:

introducing a quantity of fracturing fluid into said wellbore sufficient to fracture said formation;

introducing a treatment medium comprising liquid carbon dioxide into said wellbore; and

vaporizing at least a portion of said treatment medium.

28. The method of claim 27 wherein the steps of introducing a quantity of fracturing fluid into said wellbore and introducing a treatment medium comprising liquid carbon dioxide into said wellbore further comprise the steps of:

regulating pressure within said wellbore and said formation such that at least a portion of said treatment medium remains in a liquid state following injection into said wellbore;

inserting a length of tubing into said wellbore such that an annulus is created between said tubing and said wellbore;

pumping said treatment medium through said tubing;

pumping said fracturing fluid into said annulus;

injecting said treatment medium into said fracturing fluid to create a second fluid;

impinging said second fluid against said formation;

creating at least one fracture in said formation;

driving said second fluid into said formation; and

releasing said pressure within said wellbore.

29. The method of claim 28 wherein said fracturing fluid comprises proppant.

30. The method of claim 28 wherein the step of releasing said pressure within said wellbore vaporizes at least a portion of said second fluid, wherein said vaporized second fluid removes undesirable materials and/or water from said wellbore.

31. The method of claim 28 wherein said tubing is coiled tubing.

32. The method of claim 28 wherein the step of injecting said treatment medium into said fracturing fluid further comprises the step of injecting said treatment medium through means for focusing said treatment medium.

33. The method of claim 28 wherein said treatment medium comprising liquid carbon dioxide is introduced at a pressure of at least 2,000 psi.

34. The method of claim 28 wherein said wellbore further comprises a casing extending for at least a portion of the length of said wellbore.

35. The method of claim 28 wherein said annulus contains fracturing fluid, further comprising the steps of:

circulating additional said treatment medium down said tubing such that it exits said tubing at a first position;

vaporizing at least a portion of said treatment medium; and

driving said fracturing fluid from said annulus.

36. The method of claim 35 further comprising the steps of:

inserting additional said tubing into said wellbore such that said treatment medium exits said tubing at a second position which is deeper in said wellbore than said first position;

repeating said steps of circulating additional said treatment medium, vaporizing at least a portion of said treatment medium, and driving said fluid from said annulus; and

repeating said steps of inserting additional said tubing and circulating additional said treatment medium, vaporizing at least a portion of said treatment medium, and driving said fluid from said annulus until said formation pressure is sufficient to overcome said hydraulic head of said fluid in said annulus.

37. A wellbore treatment medium comprising liquid carbon dioxide and alcohol, surfactant, corrosion inhibitor, acid, iron-control chemical abrasive, acid, and/or biocide.

38. The wellbore treatment medium of claim 37 in the following proportions by volume:

from about 84.5% to 100% liquid carbon dioxide, from about 0 to 15% alcohol; and

from about 0 to 0.5% surfactant.

39. An apparatus for introducing a treatment medium into desired space comprising:

a storage means for storing a quantity of a treatment medium;

a pumping means for delivering said treatment medium to a transport means;

said transport means inserted into said space and operable to transport a quantity of said treatment medium to a location within said space; and

means for directing said treatment medium onto a location within said space;

wherein said treatment medium is comprised of liquid carbon dioxide and said space is defined by at least a portion of a wellbore, a casing within said wellbore, a region of a wellbore located in a hydrocarbon bearing formation adjacent a volume of said hydrocarbon bearing formation to be fractured and/or at least a portion of a hydrocarbon bearing formation near said wellbore.

40. The apparatus of claim 39 wherein said means for directing said treatment medium comprises a jetting tool.

41. The apparatus of claim 39 wherein said transport means comprises flexible tubing.

42. The apparatus of claim 41 further comprising means for measuring the position of said tubing inserted into said wellbore.

43. The apparatus of claim 39 wherein said pumping means is capable of pumping said treatment medium comprising liquid carbon dioxide and abrasive such that at least a portion of said treatment medium remains in a liquid state.

44. The apparatus of claim 39 further comprising means for regulating pressure within at least one of said wellbore and said formation wherein said pressure within said formation is maintained below said fracturing pressure.

45. An apparatus for hydraulically fracturing a fluid bearing formation having a wellbore therein comprising:

a first pumping means for delivering a treatment medium comprising liquid carbon dioxide to a first transport means;

a second pumping means for delivering a fracturing fluid to a second transport means;

said second transport means inserted into said wellbore;

said first transport means inserted into said second transport means and operable to transport a quantity of said treatment medium to a location within said second transport means; and

means for directing said treatment medium such that it mixes with said fracturing fluid producing a second fracturing fluid and said second fracturing fluid impinging a fluid bearing formation.

46. The apparatus of claim 45 wherein said means for directing said treatment medium comprises a jetting tool.

47. The apparatus of claim 45 wherein said first transport means comprises flexible tubing.

48. The apparatus of claim 47 further comprising means for measuring the position of said tubing inserted into said second transport means.

49. The apparatus of claim 45 wherein said first pumping means is capable of pumping said treatment medium comprising liquid carbon dioxide such that at least a portion of said treatment medium remains in a liquid state.