Patent ID: 8355623

Claim:
A heater configured to heat a hydrocarbon containing formation, comprising: a ferromagnetic member; an electrical conductor electrically coupled to the ferromagnetic member, the electrical conductor configured to conduct a majority of time-varying electrical current passing through the heater at about 25° C.; wherein the heater is configured to provide a first heat output below the Curie temperature of the ferromagnetic member, and the heater is configured to automatically provide a second heat output approximately at and above the Curie temperature of the ferromagnetic member, the second heat output being reduced compared to the first heat output; wherein the electrical conductor provides a majority of the mechanical strength to support the heater at or near the Curie temperature of the ferromagnetic member; wherein the heater is configured to allow heat to transfer from the heater to a hydrocarbon containing layer in the formation such that heat transfers from the heater to hydrocarbons in the hydrocarbon containing layer to at least mobilize some hydrocarbons in the layer; and wherein the heater is located in a heater well extending from a surface of the earth through an overburden of the formation and into the hydrocarbon containing layer in the formation.