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Temperature limited heaters with thermally conductive fluid used to heat subsurface formations

  • US 7,383,877 B2
  • Filed: 04/22/2005
  • Issued: 06/10/2008
  • Est. Priority Date: 04/23/2004
  • Status: Expired due to Fees
First Claim
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1. A system, comprising:

  • a heater comprising one or more electrical conductors, the heater configured to generate a heat output during application of electrical current to the heater, wherein the heater comprises a ferromagnetic material, and wherein the ferromagnetic material at least partially surrounds a non-ferromagnetic material;

    a conduit at least partially surrounding the heater;

    a fluid located in a space between the heater and the conduit, wherein the fluid has a higher thermal conductivity than air at standard temperature and pressure (STP) (0°

    C. and 101.325 kPa); and

    wherein the system is configured to provide (a) a first heat output below a selected temperature when time-varying electrical current is applied to the heater, and (b) a second heat output near or above the selected temperature when time-varying electrical current is applied to the heater; and

    wherein the system is configured to allow heat to transfer from the heater to a part of a subsurface formation.

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