On fluid and thermal dynamics in a heterogeneous CO2 plume geothermal reservoir

Abstract

CO2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can achieve both the energy exploitation and CO2 geological sequestration. The migration pathway and the process of fluid flow within the reservoirs affect significantly a CO2 plume geothermal (CPG) system. In this study,we built three-dimensionalwellbore-reservoir coupledmodels using geological and geothermal conditions of Qingshankou Formation in Songliao Basin, China. The performance of the CPG system is evaluated in terms of the temperature, CO2 plume distribution, flow rate of production fluid, heat extraction rate, and storage of CO2. For obtaining a deeper understanding of CO2-geothermal system under realistic conditions, heterogeneity of reservoir’s hydrological properties (in terms of permeability and porosity) is taken into account. Due to the fortissimo mobility of CO2, as long as a highly permeable zone exists between the twowells, it ismore likely to flowthrough the highly permeable zone to reach the productionwell, even though the flowpath is longer.The preferential flowshortens circulation time and reduces heat-exchange area, probably leading to early thermal breakthrough, which makes the production fluid temperature decrease rapidly.The analyses of flow dynamics of CO2-water fluid and heat may be useful for future design of a CO2-based geothermal development system.