TEMPERATURE LIMITED HEATERS WITH THERMALLY CONDUCTIVE FLUID USED TO HEAT SUBSURFACE FORMATIONS

摘要

The invention provides a system that includes a heater comprising one or more electrical conductors. The heater is configured to generate a heat output during application of electrical current to the heater. The heater comprises a ferromagnetic material. A conduit at least partially surrounds the heater. A fluid is located in a space between the heater and the conduit. The fluid has a higher thermal conductivity than air at standard temperature and pressure (STP) (0 °C and 101.325 kPa). The system is configured to provide (a) a first heat output below a selected temperature when time-varying electrical current is applied to the heater, and (b) a second heat output near or above the selected temperature when time-varying electrical current is applied to the heater.