Geothermal Exploitation with Considering CO2 Mineral Sequestration in High Temperature Depleted Gas Reservoir by CO2 Injection

High temperature depleted gas reservoir has the huge potential of heat mining. In this article, the method of geothermal energy exploitation in high temperature depleted gas reservoir by injection of supercritical CO2 was proposed based on the analysis of thermal properties of supercritical CO2 and the conventional heat transmission fluid-H2O. Meanwhile, reservoir numerical simulations were conducted to analyze the heat mining capacity of supercritical CO2 and related influence factors in high temperature depleted gas reservoir. The results show that this method not only can exploit geothermal energy, but also enhance the gas ultimate recovery and achieve the CO2 geological storage. Compared with the geothermal energy exploitation in water reservoir using water (100?, 35MPa), the method of geothermal energy exploitation in high temperature depleted gas reservoir (100?, 35MPa) using supercritical CO2 can achieve high-speed geothermal energy exploitation (the heat mining capacity of supercritical CO2 is one and half times heat mining capacity of water), and this method can drastically reduce initial investment using the existing well pattern so that the high-efficient development of high temperature gas reservoir can be achieved. Reaction flow simulations in typical gas reservoir were also conducted to analyze the CO2-brine-rock geochemical reactions. The results indicate that CO2 mineral sequestration cannot be ignored in the high temperature gas reservoir, which has a certain effect on CO2 storage and heat transmission. The technology of geothermal energy exploitation in high temperature depleted gas reservoir by injection of supercritical CO2 can further enhance the development value of the gas reservoir and prolongs the gas reservoir working life, which is favorable for the technology progress about geothermal development and CO2 geological storage.