The potential of coupled carbon storage and geothermal extraction in a CO2-enhanced geothermal system: a review

The increasing demand for energy makes it difficult to replace fossil fuels with low-carbon energy sources in the short term, and the large amount of CO(2)emitted by fossil fuel combustion increases global warming. Carbon capture and storage (CCS) technologies for reducing CO(2)emissions in power plants and industrial processes have been developed. High costs and security issues limit industrial applications of these technologies, so an alternative for carbon reduction is needed, i.e., CO(2)as a working fluid for coupled carbon storage and geothermal extraction in an Enhanced Geothermal System (EGS). We describe the status of global carbon emissions, CCS technologies, and their challenges. The characteristics of CO(2)as a working fluid are compared from thermophysical and thermodynamic perspectives, and the solubility of CO(2)in reservoir fluids with different ionic strengths, pressures, and temperatures is analyzed. The influence of artificial stimulation on the permeability of an EGS reservoir is described. Through heat extraction experiment of water alternating supercritical CO2(SCCO2) cycle injection, the effects of CO2-fluid-rock interactions on the reservoir's structure and of mineral dissolution and precipitation on geological CO(2)storage are analyzed. We summarize the application prospects for this alternative and the challenges of future application.