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Geologically Sequestered Carbon Dioxide as a Geothermal Heat Mining Fluid — Applications to Enhanced Oil Recovery Operations

Randolph, Jimmy B.

Recent geotechnical numerical modeling has shown that geothermal heat can be efficiently mined by circulating carbon dioxide through deep, naturally permeable sedimentary rock formations. This method, called CO2 Plume Geothermal (CPG), targets the same geologic reservoirs that are suitable for saline aquifer CO2 sequestration or enhanced oil/hydrocarbon recovery (EOR).

Previous studies have focused on CO2-based heat mining from saline aquifers for the purpose of electricity generation, whereas here we present new research that analyzes other potential CPG applications. In particular, EOR operations that use CO2 floods provide excellent opportunities for economically-favorable geothermal energy recovery, assuming sufficiently-high subsurface temperatures or the presence of waste energy in surface operations, because the majority of costly infrastructure (i.e., wells) is in place. Additionally, recovery of heat energy from CO2 offers significant advantages over traditional recovery from produced brine; for example, decreased power system footprint and increased operating efficiency. Moreover, the subsurface characteristics that make a site suitable for conventional hydrocarbon recovery -- a moderately permeable reservoir overlain by a low-permeability capping feature -- help ensure that fluid can be circulated for heat extraction while preventing unfavorable CO2 migration. While heat extraction from the CO2 + water/brine + hydrocarbon EOR production stream can be challenging, the value of heat and/or power production in offsetting EOR field operating costs and extending field lifespan can be significant.


AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013