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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
First Claim
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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.

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