Doublet huff and puff: A new technology for efficient geological CO2 sequestration and stable geothermal recovery

Carbon dioxide (CO2) emission into the atmosphere has been increasing due to the increased energy demand worldwide, significantly contributing to global warming. Therefore, capturing and permanently storing CO2 while developing renewable energy is crucial. Geothermal energy is clean and renewable and essential for decarbonizing the energy sector. This study develops a novel doublet huff-and-puff (DHP) technology for geothermal development to store super-critical CO2 (SC-CO2) and extract geothermal energy. Inspired by the huff-and-puff technology of the petroleum industry, DHP adopts a pair of wells with upper and lower perforations implemented in both, and inflow control valves (ICV) control the status of the perforations and the injection and production operating cycles. To investigate the energy recovery and storage capacity of SC-CO2 in geothermal reservoirs, we use a thermo-hydro-mechanical (THM) model to study DHP and compare it with the existing CO2 plume geothermal (CPG). The simulation results reveal that, in DHP, the produced fluid temperature after 40 years of production decreases only by 15.67% of the initial reservoir temperature (T0), whereas that in CPG decreases by an average of 26.87% of T0. Regarding the recovered energy, DHP can deliver an average of 78.83% more net heat energy than CPG. Moreover, DHP has no CO2 breakthrough for 40 years, whereas the CPG experiences a CO2 plume establishment with a breakthrough in the first 2.96 years. Further, we conduct a Levelized Cost of Energy (LCOE) analysis, finding that DHP decreases by an average of 21.23% compared to CPG. Therefore, DHP has at least three advantages compared to CPG: (1) DHP has a higher produced fluid temperature and recovered energy than CPG; (2) DHP has a more stable migration of the cold SC-CO2 plume without CO2 breakthrough in production than that in CPG; (3) DHP is more economical than CPG. The proposed DHP is a promising technology to produce geothermal energy efficiently and store store CO2 effectively in the subsurface.