Enabling CO2 Plume Geothermal: Key Geological, Reservoir, and Operational Considerations
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ABSTRACTTo investigate ways of advancing CO2 plume geothermal (CPG), we have examined key geological, reservoir, geomechanical, and operational considerations. We use a three-dimensional numerical reservoir simulator to model the impact of each parameter studied on the injectivity and productivity indices for CO2 plume geothermal systems. In addition, we use a coupled thermohydromechanical model to understand if the process might induce fracturing or seismicity. The result showed that the top of the reservoir, the formation porosity, and the formation thickness are the top three factors impacting the productivity index and injectivity index of CPG systems. We also note that produced CO2 is less than the injected CO2 due to trapping mechanisms and bypassed CO2. Lower permeability and anisotropy were more favorable for the given reservoir and well configuration. From a geological perspective, sensitivity analyses reveal the influence of dip on CO2 extraction and the need for optimal well placement. Elastic-brittle analysis suggests that reservoir fracturing and microseismicity may not occur during injection. However, microseismicity may occur during production, thus providing some guidance on how operators may want to optimize monitoring strategies.INTRODUCTIONThe apparent high cost and lack of economic attractiveness of carbon capture utilization and storage (CCUS) projects have been perceived as a challenge for the large-scale deployment of numerous CO2 capture projects (Shen et al. 2022 and Gibbins et al. 2008). Budinis et al. (2018) suggest that the ability to utilize and sequester captured CO2 could enhance the economic viability of CCUS. Researchers such as Brown (2000), Pruess (2006), Luo and Jiang (2014), and Okoroafor et al. (2022) have investigated the thermal performance of an enhanced geothermal system (EGS) using supercritical CO2, which has shown promise for heat mining due to the favorable thermophysical properties of CO2 in its supercritical state. However, unlike the complex fracture system of the EGS model, the CO2 plume geothermal system takes advantage of CO2's greater compressibility, expansibility, and lower viscosity when injected into sedimentary rocks. Fluid loss in the system indirectly serves the purpose of CO2 geological storage, as Randolph et al. (2010, 2011) observed.
