WO/2004/038173 is referenced by 4 patents.

A method described includes applying an alternating electrical current to one or more electrical conductors (112). The electrical conductors may be located in a subsurface or a subsurface wellbore. The electrical conductors may provide an electrically resistive heat output upon application of the alternating electrical current. At least one of the electrical conductors may include an electrically resistive ferromagnetic material. The electrically resistive ferromagnetic material may provide a reduced amount of heat above or near a selected temperature. Heat may be allowed to transfer from the electrically resistive ferromagnetic material to a part of the subsurface or the subsurface wellbore.

Title
Temperature limited heaters for heating subsurface formations or wellbores
Application Number
PCT/US2003/033851
Publication Number
2004/038173
Application Date
October 24, 2003
Publication Date
May 6, 2004
Inventor
Carl Jr Frederick Gordon
Menotti James Louis
Son Jaime Santos
Harris Christopher Kelvin
Sandberg Chester Ledlie
Vinegar Harold J
Agent
CHRISTENSEN Del S
Assignee
Shell Canada
Shell Internationale Research Maatschappij
IPC
E21B 43/24
E21B 36/04
E21B 36/02
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