Abstract: A method and apparatus for recovering oil from an oil bearing formation utilizing steam injected into the formation. A working fluid is heated at the surface to produce a reversible, chemical reaction, particularly a reforming reaction in a reforming/methanation reaction cycle. The products of the reforming reaction are transported at near ambient temperatures to a downhole heat exchanger through which water is circulated. There a catalyst triggers the methanation reaction, liberating heat energy to convert the water to steam. The products of the methanation reaction are recirculated to the surface to repeat the cycle. In one embodiment the products of the methanation reaction are injected into the formation along with the steam. Various catalysts, and various systems for heating the working fluid are disclosed.

Abstract: A downhole steam apparatus for location within the casing of a well borehole to facilitate oil recovery. A housing adapted to be lowered into the borehole includes a combustor for mixing and burning fuel and air, and a heat exchanger having an array of water tubes exposed to the heated gases from the combustor for converting water into steam. The steam is injected downwardly into the borehole, and the spent gases pass into the annulus between the casing and the housing. An expansible packer seals off the annulus between the steam injection area and the spent gas injection area. Compressed air for combustion is supplied at the lower spent gas pressure. Various arrangements are disclosed for the water tube array in the heat exchanger.