Abstract: A method for measuring temperatures of a hydrocarbon stratum subjected to RF electromagnetic energy includes in one embodiment sensing the temperature at different positions within an inner conductor of an applicator used to radiate the RF electromagnetic energy into the hydrocarbon stratum. In another embodiment, the temperature measurements are made from a borehole which is utilized to obtain hydrocarbon fluids resulting from the retorting of the hydrocarbon stratum in which the sensing is done in different positions within the producing borehole and in the vicinity of the hydrocarbon stratum. Electrical signals representative of the sensed temperatures are provided. The electrical signals are conducted from the sensing positions to the surface of the earth. An RF voltage which combines with the electrical signals is decoupled from the electrical signals. An indication of the temperatures is provided in accordance with the decoupled electrical signals.

Abstract: A coaxially fed applicator for in situ RF heating of subsurface bodies with a coaxial choke structure for reducing outer conductor RF currents adjacent the radiator. The outer conductor of the coaxial transmission line supplying RF energy to the radiator terminates in a coaxial structure comprising a section of coaxial line extending toward the RF radiator from the termination for a distance approaching a quarter wavelength at the RF frequency and a coaxial stub extending back along the coaxial line outer conductor from the termination for a distance less than a quarter wavelength at said frequency. The central conductor of the coaxial transmission line is connected to an enlarged coaxial structure approximately a quarter of a wavelength long in a region beyond the end of the outer conductor coaxial choking structure.