Triaxial temperature limited heater

• US 7,370,704 B2
• Filed: 04/22/2005
• Issued: 05/13/2008
• Est. Priority Date: 04/23/2004
• Status: Expired due to Fees

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Harris, Christopher Kelvin
• Primary Examiner(s): KRECK, JOHN J
• Application Number:
  US11/113,342
• Publication Number:
  US 20050269094A1
• Time in Patent Office: 1,117 Days
• Field of Search: 166/302, 166/56
• US Class Current: 166/302
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/12 Methods or apparatus for controlling the flow of the obtained fluid to or in wells E21B43/25 takes precedence; valve arrangements E21B34/00
• CPC Class Codes: E21B 43/122 Gas lift
• 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: E21B 43/2405 in association with fracturing or crevice forming processes E21B43/247 takes precedence
• CPC Class Codes: E21B 43/38 in the well
• CPC Class Codes: H05B 3/141 Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds

Abstract

Certain embodiments provide a heater. The heater includes an inner electrical conductor. A heater section at least partially surrounds the inner electrical conductor. The heater section is configured to generate an electrically resistive heat output during application of time-varying electrical current to the heater section. The heater section includes ferromagnetic material. An outer electrical conductor at least partially surrounds the heater section. An applied time-varying electrical current is configured to propagate through the inner electrical conductor and the outer electrical conductor in substantially the same direction. The applied time-varying electrical current is configured to propagate through the heater section in a substantially opposite direction. The heater provides a first heat output when time-varying electrical current is applied to the heater below a selected temperature, and a second heat output approximately at and above the selected temperature during use. The second heat output is reduced compared to the first heat output.

Claims

1. A method of heating a subsurface formation, comprising:

providing time-varying electrical current in a first direction to a heater section to provide an electrically resistive heat output, wherein the heater section comprises ferromagnetic material;

allowing electrical current to propagate in a second direction through an inner electrical conductor and an outer electrical conductor, wherein the heater section at least partially surrounds the inner electrical conductor and is at least partially surrounded by the outer electrical conductor;

wherein the provided time-varying electrical current (a) provides a first heat output when the heater section below a selected temperature, and (b) provides a second heat output when the heater section is approximately at and above the selected temperature, the second heat output being reduced compared to the first heat output; and

allowing heat to transfer from the heater section to at least part of the subsurface formation.

2. The method of claim 1, wherein the inner electrical conductor comprises an electrically resistive, substantially non-ferromagnetic material.

3. The method of claim 1, wherein the outer electrical conductor comprises an electrically resistive, substantially non-ferromagnetic material.

4. The method of claim 1, wherein the provided time-varying electrical current comprises AC.

5. The method of claim 1, wherein the provided time-varying electrical current comprises modulated DC.

6. The method of claim 1, further comprising providing the electrical current from an AC power supply.

7. The method of claim 1, further comprising providing the electrical current from a modulated DC power supply.

8. The method of claim 1, wherein the second heat output is provided without adjusting the amperage of the electrical current applied to the heater section.

9. The method of claim 1, wherein the second heat output is at most 900% of the first heat output, the first heat output being at about 50°

C. below the selected temperature.

10. The method of claim 1, further comprising placing the heater section, the inner electrical conductor, and the outer electrical conductor in a wellbore in the subsurface formation.

11. The method of claim 1, wherein the heater section is separated from the inner electrical conductor and the outer electrical conductor with an electrical insulator.

12. A method of heating a subsurface formation, comprising:

providing time-varying electrical current in a first direction to a heater section to provide an electrically resistive heat output, wherein the heater section comprises ferromagnetic material;

allowing electrical current to propagate in a second direction through an inner electrical conductor and an outer electrical conductor, the second direction being substantially opposite to the first direction, wherein the heater section at least partially surrounds the inner electrical conductor and is at least partially surrounded by the outer electrical conductor;

wherein the provided time-varying electrical current (a) provides a first heat output when the heater section below a selected temperature, and (b) provides a second heat output when the heater section is approximately at and above the selected temperature, the second heat output being reduced compared to the first heat output; and

allowing heat to transfer from the heater section to at least part of the subsurface formation.

13. The method of claim 12, wherein the inner electrical conductor comprises an electrically resistive, substantially non-ferromagnetic material.

14. The method of claim 12, wherein the outer electrical conductor comprises an electrically resistive, substantially non-ferromagnetic material.

15. The method of claim 12, wherein the provided time-varying electrical current comprises AC.

16. The method of claim 12, wherein the provided time-varying electrical current comprises modulated DC.

17. The method of claim 12, further comprising providing the electrical current from an AC power supply.

18. The method of claim 12, further comprising providing the electrical current from a modulated DC power supply.

19. The method of claim 12, wherein the second heat output is provided without adjusting the amperage of the electrical current applied to the heater section.

20. The method of claim 12, wherein the second heat output is at most 90% of the first heat output, the first heat output being at about 50°

C. below the selected temperature.

21. The method of claim 12, further comprising placing the heater section, the inner electrical conductor, and the outer electrical conductor in a wellbore in the subsurface formation.

22. The method of claim 12, wherein the heater section is separated from the inner electrical conductor and the outer electrical conductor with an electrical insulator.