Patent ID: 8224164

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 electrical conductor located in the heater well and extending from the surface and into the hydrocarbon containing layer, the electrical conductor being configured to generate an electrically resistive heat output during application of AC to the electrical conductor such that heat transfers from the electrical conductor to hydrocarbons in the hydrocarbon containing layer to at least mobilize some hydrocarbons in the layer; wherein the electrical conductor comprises an electrically resistive ferromagnetic material at least partially surrounding a non-ferromagnetic material such that the heater provides a reduced amount of heat above or near a selected temperature; an electrical insulator at least partially surrounding the electrical conductor; and a sheath at least partially surrounding the electrical insulator.