Downhole steam generator having a downhole oxidant compressor

Abstract

Apparatus and method for generation of steam in a borehole for penetration into an earth formation wherein a downhole oxidant compressor is used to compress relatively low pressure (atmospheric) oxidant, such as air, to a relatively high pressure prior to mixing with fuel for combustion. The multi-stage compressor receives motive power through a shaft driven by a gas turbine powered by the hot expanding combustion gases. The main flow of compressed oxidant passes through a velocity increasing nozzle formed by a reduced central section of the compressor housing. An oxidant bypass feedpipe leading to peripheral oxidant injection nozzles of the combustion chamber are also provided. The downhole compressor allows effective steam generation in deep wells without need for high pressure surface compressors. Feedback preheater means are provided for preheating fuel in a preheat chamber. Preheating of the water occurs in both a water feed line running from aboveground and in a countercurrent water flow channel surrounding the combustor assembly. The countercurrent water flow channels advantageously serve to cool the combustion chamber wall. The water is injected through slotted inlets along the combustion chamber wall to provide an unstable boundary layer and stripping of the water from the wall for efficient steam generation. Pressure responsive doors are provided at the steam outlet for closing and sealing the combustion chamber from entry of reservoir fluids in the event of a flameout.