Pairing of an Integrated Gasification Combined Cycle Power Plant (IGCC) with CO2-EGS as a Strategy for Deployment in Arid Regions

Abstract

We explore the utility of linking an integrated gasification combined cycle (IGCC) plant with EGS. The principal attributes for this linkage is that the IGCC system generates electricity with most of the waste streams reused in the overall process and that the primary output is a stream of pure CO2 that may be used directly as a heat transfer fluid. This CO2 may be used either in EGS or as a sequestration stream into a porous aquifer with additional scavenging of heat. We explore the major components of the IGCC system related to coupling with fluid circulation within a geothermal reservoir. The principal features are that combustion of coal using oxygen (rather than air) produces an output stream of H20 and CO that may be converted to H2 and CO2. The hydrogen is available for combustion or higher-value uses and the pure stream of CO2 reduces the aquifer storage space for sequestration or may be used, as in this case, as a supply stream for EGS. In this case, thermal energy from the EGS reservoir is converted to electricity, as is the steam from the combustion of hydrogen. The IGCC system integrates the combustion of coal with generation of electricity through a steam turbine and importantly with a concentrated output stream of CO2 alone. This may be used for direct injection of CO2 into the subsurface – either for sequestration in a porous aquifer or to develop a low fracture porosity EGS reservoir. In this application we concentrate on the latter, identifying the principal attributes of performance of such a system. We note the favorable to neutral heat transfer and fluid transport characteristics of CO2 relative to water and how these impact the operational feasibility of such as system. We examine the role of fluid rock interactions as the reservoir is developed and as the CO2 displaces a water front toward the periphery of the effective reservoir. Similarly, we examine the role of these effects on rates of reservoir development and on permeability evolution and on triggered seismicity. Finally, we examine the thermal output from various reservoir geometries from longitudinal to five-spot patterns and scale the necessary linkage between CO2 output from the IGCC plant to the needs of the geothermal system, inclusive of projected fluid losses to the periphery. These discussions are relevant to the feasibility for commercialization of such linked models of IGCC and EGS.