Variable frequency temperature limited heaters

• US 8,224,163 B2
• Filed: 10/24/2003
• Issued: 07/17/2012
• Est. Priority Date: 10/24/2002
• Status: Expired due to Fees

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Sandberg, Chester Ledlie, Vinegar, Harold J., Harris, Christopher Kelvin, Son, Jaime Santos, Carl, Fredrick Gordon Jr.
• Primary Examiner(s): PAIK, SANG YEOP
• Application Number:
  US10/693,700
• Publication Number:
  US 20050006097A1
• Time in Patent Office: 3,189 Days
• Field of Search: 392301-306, 392/469, 166 60- 61, 166/302, 166/248, 219/553
• US Class Current: 392/301
• CPC Class Codes: E21B 36/008 using chemical heat generating means
• CPC Class Codes: E21B 36/02 using burners
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: H05B 2214/03 Heating of hydrocarbons

Abstract

A heater system may include an alternating current supply and an electrical conductor. Alternating current may be applied to one or more electrical conductors at a frequency between about 100 Hz and about 1000 Hz. The electrical conductors may be located in a formation. The electrical conductors may resistively heat upon application of the alternating electrical current. At least one of the electrical conductors may include an electrically resistive ferromagnetic material. The electrical conductor may provide a reduced amount of heat above or near a selected temperature. Heat may transfer from the electrical conductor to a part of formation.

Claims

1. A system configured to heat a hydrocarbon containing formation, comprising:

a heater well extending from a surface of the earth through an overburden of the formation and into a hydrocarbon containing layer in the formation;

an AC supply configured to provide AC at a frequency between about 100 Hz and about 1000 Hz;

one or more electrical conductors located in the heater well, at least one of the electrical conductors extending from the surface into the hydrocarbon containing layer, and at least one of the electrical conductors being electrically coupled to the AC supply;

at least one electrical conductor comprising an electrically resistive ferromagnetic material, the electrical conductor being configured to provide an electrically resistive heat output during application of AC to the electrical conductor, and the electrical conductor being configured to provide a reduced amount of heat above or near a selected temperature, the selected temperature being within about 50°

C. of the Curie temperature of the ferromagnetic material; and

wherein the system is configured to provide heat to the hydrocarbon containing formation such that sufficient heat transfers from at least one of the electrical conductors to hydrocarbons in the hydrocarbon containing formation to at least mobilize some hydrocarbons in the formation.

2. The system of claim 1, further comprising at least one production well extending into the hydrocarbon containing layer and configured to produce at least some of the mobilized hydrocarbons from the hydrocarbon containing layer.

3. The system of claim 1, wherein at least one electrical conductor transfers heat during use to hydrocarbons in the hydrocarbon containing layer to at least mobilize some hydrocarbons in the layer.

4. The system of claim 1, wherein at least one electrical conductor transfers heat during use to hydrocarbons in the hydrocarbon containing layer to pyrolyze at least some hydrocarbons in the layer.

5. The system of claim 1, wherein at least one of the ferromagnetic sections heats during use to a temperature of at least about 650°

C.

6. The system of claim 1, wherein the AC supply is coupled to a supply of line current, and wherein the AC supply is configured to provide AC at about three times the frequency of the line current.

7. The system of claim 1, wherein the AC supply is configured to provide AC with a frequency between about 140 Hz and about 200 Hz.

8. The system of claim 1, wherein AC supply is configured to provide AC with a frequency between about 400 Hz and about 550 Hz.

9. The system of claim 1, wherein the ferromagnetic material comprises iron, nickel, chromium, cobalt, tungsten, or a mixture thereof.

10. The system of claim 1, wherein a thickness of the ferromagnetic material is at least about ¾

of a skin depth of the AC at the Curie temperature of the ferromagnetic material.

11. The system of claim 1, wherein the heat output below the selected temperature is greater than about 400 watts per meter of the electrical conductor.

12. The system of claim 1, wherein at least a portion of at least one of the electrical conductors is longer than about 10 m.

13. The system of claim 1, wherein the system is configured to sharply reduce the heat output at or near the selected temperature.

14. The system of claim 1, wherein the system is configured such that the heat output of at least a portion of the system decreases at or near the selected temperature due to the Curie effect.

15. The system of claim 1, wherein the system is configured to apply AC of at least about 70 amps to at least one of the electrically resistive sections.

16. The system of claim 1, wherein at least one of the electrical conductors comprises a turndown ratio of at least about 2 to 1.

17. The system of claim 1, wherein the system is configured to withstand operating temperatures of about 250°

C. or above.

18. The system of claim 1, wherein the electrical conductor is configured to automatically provide the reduced amount of heat above or near the selected temperature.

19. The system of claim 1, wherein the heater well extends at least about 10 m into the hydrocarbon containing layer.

20. The system of claim 1, wherein the hydrocarbon containing layer comprises hydrocarbons configured to be treated and produced from the formation using an in situ conversion process.

21. A system configured to heat a hydrocarbon containing formation, comprising:

a heater well extending from a surface of the earth through an overburden of the formation and into a hydrocarbon containing layer in the formation;

an AC supply configured to provide AC at a frequency between about 100 Hz and about 1000 Hz;

one or more electrical conductors located in the heater well, at least one of the electrical conductors extending from the surface into the hydrocarbon containing layer, and at least one of the electrical conductors being electrically coupled to the AC supply;

at least one electrical conductor comprising an electrically resistive ferromagnetic material, the electrical conductor being configured to provide an electrically resistive heat output during application of AC to the electrical conductor, and the electrical conductor being configured to provide a reduced amount of heat above or near a selected temperature that is about 20% or less of the heat output at about 50°

C. below the selected temperature, and wherein the selected temperature is at or about the Curie temperature of the ferromagnetic material; and

wherein the system is configured to provide heat to the hydrocarbon containing formation such that sufficient heat transfers from at least one of the electrical conductors to hydrocarbons in the hydrocarbon containing formation to at least mobilize some hydrocarbons in the formation.

22. The system of claim 21, further comprising at least one production well extending into the hydrocarbon containing layer and configured to produce at least some of the mobilized hydrocarbons from the hydrocarbon containing layer.

23. The system of claim 21, wherein at least one electrical conductor transfers heat during use to hydrocarbons in the hydrocarbon containing layer to at least mobilize some hydrocarbons in the layer.

24. The system of claim 21, wherein at least one electrical conductor transfers heat during use to hydrocarbons in the hydrocarbon containing layer to pyrolyze at least some hydrocarbons in the layer.

25. The system of claim 21, wherein at least one of the ferromagnetic sections heats during use to a temperature of at least about 650°

C.

26. The system of claim 21, wherein the AC supply is coupled to a supply of line current, and wherein the AC supply is configured to provide AC at about three times the frequency of the line current.

27. The system of claim 21, wherein the AC supply is configured to provide AC with a frequency between about 140 Hz and about 200 Hz.

28. The system of claim 21, wherein AC supply is configured to provide AC with a frequency between about 400 Hz and about 550 Hz.

29. The system of claim 21, wherein the ferromagnetic material comprises iron, nickel, chromium, cobalt, tungsten, or a mixture thereof.

30. The system of claim 21, wherein a thickness of the ferromagnetic material is at least about ¾

of a skin depth of the AC at the Curie temperature of the ferromagnetic material.

31. The system of claim 21, wherein the heat output below the selected temperature is greater than about 400 watts per meter of the electrical conductor.

32. The system of claim 21, wherein at least a portion of at least one of the electrical conductors is longer than about 10 m.

33. The system of claim 21, wherein the system is configured to sharply reduce the heat output at or near the selected temperature.

34. The system of claim 21, wherein the system is configured such that the heat output of at least a portion of the system decreases at or near the selected temperature due to the Curie effect.

35. The system of claim 21, wherein the system is configured to apply AC of at least about 70 amps to at least one of the electrically resistive sections.

36. The system of claim 21, wherein at least one of the electrical conductors comprises a turndown ratio of at least about 2 to 1.

37. The system of claim 21, wherein the system is configured to withstand operating temperatures of about 250°

C. or above.

38. The system of claim 21, wherein the electrical conductor is configured to automatically provide the reduced amount of heat above or near the selected temperature.

39. The system of claim 21, wherein the heater well extends at least about 10 m into the hydrocarbon containing layer.

40. The system of claim 21, wherein the hydrocarbon containing layer comprises hydrocarbons configured to be treated and produced from the formation using an in situ conversion process.

41. A method of heating a hydrocarbon containing formation, comprising:

providing AC at a frequency between about 100 Hz and about 1000 Hz to one or more electrical conductors located in a heater well extending from a surface of the earth through an overburden of the formation and into a hydrocarbon containing layer in the formation, wherein providing the AC produces an electrically resistive heat output from the electrical conductors, at least one of the electrical conductors comprising one or more electrically resistive ferromagnetic sections;

wherein one or more of the electrically resistive ferromagnetic sections are configured to provide a reduced amount of heat above or near a selected temperature, the selected temperature being within about 50°

C. of the Curie temperature of the ferromagnetic material; and

allowing heat to transfer from the electrical conductors to hydrocarbons in the hydrocarbon containing layer to at least mobilize some hydrocarbons in the layer.

42. The method of claim 41, further comprising producing at least some of the mobilized hydrocarbons from the layer through a production well extending into the hydrocarbon containing layer.

43. The method of claim 41, wherein the transferred heat pyrolyzes at least some hydrocarbons in the hydrocarbon containing layer.

44. The method of claim 43, further comprising producing at least some of the pyrolyzed hydrocarbons from the layer through a production well extending into the hydrocarbon containing layer.

45. The method of claim 41, wherein at least one of the ferromagnetic sections heats to a temperature of at least about 650°

C.

46. The method of claim 41, further comprising providing an initial electrically resistive heat output when the electrical conductor providing the heat output is at least about 50°

C. below the selected temperature, and automatically providing the reduced amount of heat above or near the selected temperature.

47. The method of claim 41, further comprising providing the AC at about three times the frequency of line current from an AC supply.

48. The method of claim 41, further comprising providing the AC at a frequency between about 140 Hz and about 200 Hz.

49. The method of claim 41, further comprising providing the AC at a frequency between about 400 Hz and about 550 Hz.

50. The method of claim 41, wherein a thickness of at least one of the ferromagnetic sections is at least about ¾

of a skin depth of the AC at the Curie temperature of the ferromagnetic material.

51. The method of claim 41, further comprising providing a reduced amount of heat above or near the selected temperature of less than about 400 watts per meter of length of the electrical conductor.

52. The method of claim 41, further comprising controlling a skin depth in the electrical conductor by controlling a frequency of the AC applied to the electrical conductor.

53. The method of claim 41, further comprising controlling the amount of current applied to the electrical conductors to control an amount of heat provided by at least one of the electrically resistive sections.

54. The method of claim 41, further comprising applying current of at least about 70 amps to the electrical conductor.

55. The method of claim 41, wherein the heater well extends at least about 10 m into the hydrocarbon containing layer.

56. The method of claim 41, wherein the hydrocarbon containing layer comprises hydrocarbons configured to be treated and produced from the formation using an in situ conversion process.