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Varying properties along lengths of temperature limited heaters

  • US 7,986,869 B2
  • Filed: 04/21/2006
  • Issued: 07/26/2011
  • Est. Priority Date: 04/22/2005
  • Status: Expired due to Fees
First Claim
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1. A method for heating a subsurface formation, comprising:

  • applying an electrical current to an elongated heater such that the heater provides an electrically resistive heat output, wherein the elongated heater comprises two or more portions along the length of the heater that have different power outputs, at least one portion of the elongated heater comprising at least one temperature limited portion with at least one selected temperature at which the portion provides a reduced heat output;

    providing heat to the formation with the different power outputs such that the heater heats one or more portions of the formation at one or more selected heating rates; and

    allowing the heat to transfer to a section of the formation.

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