Patent ID: 8224163

Claim:
A system configured to heat a hydrocarbon containing formation, comprising: a heater well extending from a surface of the earth through an overburden of the formation and into a hydrocarbon containing layer in the formation; an AC supply configured to provide AC at a frequency between about 100 Hz and about 1000 Hz; one or more electrical conductors located in the heater well, at least one of the electrical conductors extending from the surface into the hydrocarbon containing layer, and at least one of the electrical conductors being electrically coupled to the AC supply; at least one electrical conductor comprising an electrically resistive ferromagnetic material, the electrical conductor being configured to provide an electrically resistive heat output during application of AC to the electrical conductor, and the electrical conductor being configured to provide a reduced amount of heat above or near a selected temperature, the selected temperature being within about 50° C. of the Curie temperature of the ferromagnetic material; and wherein the system is configured to provide heat to the hydrocarbon containing formation such that sufficient heat transfers from at least one of the electrical conductors to hydrocarbons in the hydrocarbon containing formation to at least mobilize some hydrocarbons in the formation.