Resistive heater for in situ formation heating

• US 20080230219A1
• Filed: 03/07/2008
• Published: 09/25/2008
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: Robert D. Kaminsky
• Original Assignee: Robert D. Kaminsky
• Inventors: Kaminsky, Robert D.
• Granted Patent: US 8,622,133 B2
• Time in Patent Office: Days
• US Class Current: 166/248
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 41/0064 Carbon dioxide sequestration storing fluids in porous layers B65G5/005
• CPC Class Codes: E21B 43/17 Interconnecting two or more wells by fracturing or otherwise attacking the formation E21B43/2405, E21B43/247 take precedence
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: E21B 43/267 reinforcing fractures by propping
• CPC Class Codes: E21B 43/305 comprising at least one inclined or horizontal well
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Improved methods for heating a subsurface formation using an electrical resistance heater are provided. Preferably, the subsurface formation is an organic-rich rock formation, including, for example, an oil shale formation. One embodiment of the method includes providing an electrically conductive first member in a wellbore located in a subsurface formation, and also providing an electrically conductive second member in the wellbore. The method also includes providing an electrically conductive granular material in the wellbore. The granular material is positioned so as to provide an electrical connection between the first member and the second member. An electrical current is established across the first member, the granular material and the second member so as to generate resistive heat within the granular material. The surrounding subsurface formation is thereby conductively heated so as to cause formation hydrocarbons in the formation to be heated, and in some cases, pyrolyzed to form hydrocarbon fluids.

Claims

1. A method for heating a subsurface formation using electrically resistive heat, comprising:

providing a first wellbore located at least partially within a subsurface formation, the first wellbore having an electrically conductive first member, an electrically conductive second member, and an electrically conductive first granular material in the first wellbore, wherein the first granular material is positioned to provide electrical communication between the first member and the second member;

providing a second wellbore located at least partially within the subsurface formation, the second wellbore having an electrically conductive third member, an electrically conductive fourth member, and an electrically conductive second granular material in the second wellbore, wherein the second granular material is positioned to provide electrical communication between the third member and the fourth member;

passing a first electrical current through the first member, the first granular material and the second member, thereby generating first heat, the generated first heat produced primarily through electrical resistive heating of the first granular material;

passing a second electrical current through the third member, the second granular material and the fourth member, thereby generating second heat, the generated second heat produced primarily through electrical resistive heating of the second granular material; and

heating formation hydrocarbons located substantially equidistant from the first wellbore and the second wellbore primarily with the generated first heat, second heat or both.

2. The method of claim 1, wherein the subsurface formation is an organic-rich rock formation.

3. The method of claim 2, wherein the subsurface formation contains heavy hydrocarbons.

4. The method of claim 2, wherein the subsurface formation is an oil shale formation and the generated first heat, second heat or both cause the formation hydrocarbons to be substantially pyrolyzed to form hydrocarbon fluids.

5. The method of claim 4, wherein:

the generated first heat is comprised of electrical resistive heating of the first member, the first granular material and the second member; and

at least 75% of the generated first heat is generated by electrical resistive heating of the first granular material.

6. The method of claim 4, wherein the first granular material contacts the first member and the second member.

7. The method of claim 4, wherein there is no substantial flow of hydrocarbon fluid through the first granular material.

8. The method of claim 4, wherein the first granular material comprises calcined petroleum coke, graphite, metal oxides, or ceramic particles coated with thin metal layers.

9. The method of claim 4, wherein the first electrical current flows substantially longitudinally through the first granular material.

10. The method of claim 9, where the first granular material has an in-place electrical resistivity of about 10⁻

5 to 10<sup>−

2</sup> ohm-meters.

11. The method of claim 4, wherein the first electrical current flows radially through the first granular material.

12. The method of claim 11, wherein the first granular material has an in-place electrical resistivity of about 100 to 10,000 ohm-meters.

13. The method of claim 4, wherein the first wellbore is substantially vertical.

14. The method of claim 4, wherein a lower portion of the first wellbore is deviated.

15. The method of claim 4, wherein the first member defines a well pipe set in the first wellbore.

16. The method of claim 15, wherein the well pipe is a string of casing, a string of tubing, or combinations thereof.

17. The method of claim 16, wherein the second member is located at least partially within the well pipe.

18. The method of claim 4, wherein the first member and the second member each comprise an elongated rod, with the first member terminating at a first depth, and the second member terminating at a second lower depth within the subsurface formation.

19. The method of claim 5, wherein:

the first member comprises a well pipe string located in the first wellbore to a first depth, the well pipe string thereby serving as at least a portion of the first member;

the second member comprises a second conductive string located within the well pipe string to a second depth below the first depth, the second conductive string thereby serving as at least a portion of the second member; and

the first conductive granular material is positioned in the first wellbore around the second conductive string at and below the first depth.

20. The method of claim 19, wherein:

the well pipe string comprises an upper portion that is electrically nonconductive, and a lower portion that is electrically conductive; and

the first member further comprises an electrically conductive wire or cable providing electrical communication between the lower portion of the well pipe string and a power source at a surface.

21. The method of claim 19, further comprising:

providing an electrically conductive wire or cable in the first wellbore proximate an upper portion of the first granular material; and

electrically connecting the electrically conductive wire or cable to the well pipe string, the well pipe string and the wire or cable thereby serving as at least a portion of the first member.

22. The method of claim 19, wherein:

the second depth is near the bottom of the first wellbore;

the second conductive string is insulated with an electrically insulating material from at least the first depth to a third depth, the third depth being between the first depth and the second depth so that at least a lower portion of the second conductive string is left uninsulated; and

the step of passing a first electrical current comprises applying a voltage across the well pipe string and the lower portion of the second conductive string, thereby establishing the first electrical current through the first granular material and generating first heat through electrical resistive heating of the first granular material.

23. The method of claim 19, wherein:

the first depth and the second depth are both near the bottom of the wellbore;

an annular region is defined between the well pipe string and the second conductive string; and

the step of passing a first electrical current includes establishing an electrical current radially through the first granular material, thereby generating first heat through electrical resistive heating of the first granular material.

24. The method of claim 23, wherein:

the subsurface formation contains two separate oil shale zones;

the first granular material is placed within the annular region adjacent each of the two separate oil shale zones; and

the first granular material is separated within the annular region by slugs of substantially electrically insulating material.

25. The method of claim 24, wherein the slugs of insulating material comprise insulating granular material made up of at least one of quartz sand, ceramic particles, clays, and gravel.

26. The method of claim 19, wherein the first granular material comprises one or more slugs of highly conductive granular material interspersed between slugs of less conductive granular material so that only subsections of the wellbore receiving the less conductive granular material will be substantially heated.

27. The method of claim 4, wherein the resistivity of the first member, the second member, or both is less than about 0.00001 0.00001 (1×

10<sup>−

5</sup>) Ohm-meters.

28. A method for heating a subsurface formation, comprising:

forming a wellbore to the subsurface formation;

placing a string of conductive casing proximate the bottom of the wellbore;

running an elongated conductive element into the wellbore and within the string of conductive casing, thereby forming an annular region between the string of conductive casing and the elongated conductive element;

filling at least a part of the annular region with a conductive granular material to act as a resistive heating element;

radially passing an electrical current through the string of conductive casing, through the granular material, and through the elongated conductive element within the casing in order to generate resistive heat within the granular material; and

continuing to radially pass electricity through the granular material to generate additional resistive heat in order to cause in situ pyrolysis of at least some formation hydrocarbons, thereby forming hydrocarbon fluids.

29. The method of claim 28, wherein the formation hydrocarbons comprise oil shale.

30. The method of claim 29, wherein the elongated conductive element comprises a metal rod, a metal tubing, a cable or a metal wire.

31. The method of claim 29, wherein:

the wellbore is substantially vertical; and

the conductive element hangs within the surrounding string of casing.

32. The method of claim 31, wherein the elongated conductive element is centralized in the string of conductive casing using electrically nonconductive centralizers, the centralizers being sized to slidably engage an inner diameter of the surrounding string of casing while permitting relative longitudinal movement between the string of casing and the conductive element.

33. The method of claim 29, wherein the granular material is a mixture of two or more component granular materials each with different electrical conductivity to adjust a bulk resistivity of the mixture.

34. The method of claim 29, wherein the granular material is mixed with a binder which sets after being placed in the wellbore.

35. The method of claim 34, wherein the binder is cement.

36. The method of claim 32, wherein the centralizers are spaced at least twenty feet apart.

37. The method of claim 32, wherein the bottom of the string of casing is sealed to formation gases.

38. The method of claim 37, wherein the wellbore is pressurized with an inert gas.

39. The method of claim 29, wherein the resistive heating element has a bulk resistance that is higher than the electrical resistance of the string of conductive casing and the elongated conductive element so that resistive heat is generated primarily within the granular material when a current is passed through the string of conductive casing, the granular material and the elongated conductive element.

40. A method for heating an organic-rich rock formation, comprising:

providing a plurality of heater wells, each of the plurality of heater wells comprising;

a) a first wellbore located at least partially within the organic-rich rock formation;

an electrically conductive first member located in the first wellbore;

b) a second wellbore, the second wellbore having a bottom portion that intersects the first wellbore;

c) an electrically conductive second member located in the second wellbore; and

d) an electrically conductive granular material filling at least a part of each of the first and second wellbores so as to provide an electrical connection between the first member in the first wellbore and the second member in the second wellbore, the granular material thereby forming a granular mass and acting as a resistive heating element, the first member, granular material and second member thereby forming an electrical flow path;

passing electrical current through each electrical flow path in order to generate heat primarily via electrical resistive heating within the granular material;

transferring, by thermal conduction, at least a portion of the generated heat into the organic-rich rock formation, thereby forming a heated volume of the organic-rich rock formation, the heated volume being defined at it'"'"'s extremities by a plurality of the granular masses; and

heating a majority of the formation hydrocarbons located in the heated volume of the organic-rich rock formation primarily with the generated heat, thereby causing the formation hydrocarbons to be substantially pyrolyzed to form hydrocarbon fluids.

41. The method of claim 40, wherein the organic-rich rock formation comprises kerogen.

42. The method of claim 41, wherein the first member and the second member comprise a casing, a metal rod, a metal wire, or combinations thereof.

43. The method of claim 41, wherein the first wellbore is substantially vertical and a bottom portion of the second wellbore is deviated.

44. The method of claim 41, wherein the granular material has a bulk electrical resistance that is greater than an electrical resistance of the first member and an electrical resistance of the second member.

45. The method of claim 44, further comprising:

providing a third wellbore, the third wellbore also having a bottom portion that intersects the first wellbore;

running an electrically conductive third member into the third wellbore;

filling at least a part of the third wellbore with the electrically conductive granular material so as to provide an electrical connection between the third member and the first and second members; and

wherein the step of passing an electrical current further comprises passing an electrical current through the third member in the third wellbore.

46. The method of claim 45, wherein:

the granular material has a bulk electrical resistance that is greater than an electrical resistance of the third member; and

the step of passing an electrical current is performed by flowing a three-phase current from a three-phase power source.

47. The method of claim 41, wherein the first and second wellbores are spaced from about 10 to 120 feet apart.

48. The method of claim 40, further comprising:

testing the electrical conductivity of the electrical flow path.

49. A method of producing a hydrocarbon fluid, comprising:

heating an organic-rich rock formation in situ primarily using heat generated by electrical resistive heating of a granular material included in an electrical resistance heater, thereby producing a heated portion of the organic-rich rock formation;

controlling the rate of heat generation such that the electrical conductivity of a majority of the heated portion of the organic-rich rock formation does not increase substantially; and

producing a hydrocarbon fluid from the organic-rich rock formation, the hydrocarbon fluid having been generated as a result of heating and pyrolysis of formation hydrocarbons located in the heated portion of the organic-rich rock formation, the heating and pyrolysis resulting primarily from the heat generated by electrical resistive heating of the granular material, wherein the electrical resistance heater is formed by;

passing electricity through a conductive granular material to generate resistive heat within the granular material, the granular material being disposed between and within at least two adjacent wellbores completed at least partially within the organic-rich rock formation, the granular material providing electrical communication between the wellbores, wherein a majority of the resistive heat is generated within the granular material; and

transferring, by thermal conduction, at least a portion of the resistive heat into the organic-rich rock formation in order to cause in situ pyrolysis of the formation hydrocarbons located in the heated portion of the organic-rich rock formation to form the hydrocarbon fluid.

50. A method of producing a hydrocarbon fluid, comprising:

heating an organic-rich rock formation in situ primarily using heat generated by electrical resistive heating of a granular material included in an electrical resistance heater, thereby producing a heated portion of the organic-rich rock formation;

controlling the rate of heat generation such that the electrical conductivity of a majority of the heated portion of the organic-rich rock formation does not increase substantially; and

producing a hydrocarbon fluid from the organic-rich rock formation, the hydrocarbon fluid having been at least partially generated as a result of heating and pyrolysis of formation hydrocarbons located in the heated portion of the organic-rich rock formation, the heating and pyrolysis resulting primarily from the heat generated by electrical resistive heating of the granular material, wherein the electrical resistance heater is formed by;

a) providing a wellbore located at least partially within the organic-rich rock, the wellbore having an electrically conductive first member, an electrically conductive second member, and an electrically conductive granular material in the wellbore, wherein the granular material is positioned to provide electrical communication between the first member and the second member; and

b) passing an electrical current through the first member, the granular material and the second member, thereby generating heat, the generated heat produced primarily through electrical resistive heating of the granular material.