This invention relates to improved electrical resistance heaters.
BACKGROUND OF THE INVENTION
Electrical resistance heaters suitable for heating long intervals of subterranean earth formations have been under development for many years. These heaters have been found to be useful for carbonizing hydrocarboncontaining zones for use as electrodes within reservoir formations, for enhanced oil recovery and for recovery of hydrocarbons from oil shales. U.S. Pat. No. 2,732,195 discloses a process to create electrodes utilizing a subterranean heater. The heater utilized is capable of heating an interval of 20 to 30 meters within subterranean oil shales to temperatures of 500° C. to 1000° C. Iron or chromium alloy resistors are utilized as the core heating element. These heating elements have a high resistance and relatively large voltage is required for the heater to extend over a long interval with a reasonable heat flux. It would be preferable to utilize lower resistance material. Further, it would be preferable to use a material which is malleable to permit more economical fabrication of the heater.