Feasibility of combination of CO 2 geological storage with geothermal-type water-soluble gas recovery in Yinggehai Basin, China

Carbon dioxide capture, utilization and storage (CCUS) is an important technology to combat global climate change. Carbon dioxide (CO2), a greenhouse gas, can also be used to extract lighter components from subsurface fluids in a multicomponent hydrocarbon system. In many oil and gas bearing basins, there are high temperature and high pressure aquifers saturated with methane. These aquifers are usually known as geothermal-type water-soluble gas reservoirs. The geothermal-type water-soluble gas reservoirs have great potential for coupled development to harvest thermal energy and natural gases. Additionally, the aquifers can serve as favorable sites for CO2 geological sequestration. This paper proposes a new feasible technology that combines CO2 geological sequestration with geothermal-type water-soluble gas recovery (CO2-GWSGR). This proposed technology injects CO2 into the pressurized aquifer for greenhouse gas reduction and natural gas and thermal energy development. In the Yinggehai Basin, there are rich water-soluble gas resources and some natural gas wells that produce CO2. Based on the reservoir characterization of the Yinggehai Basin, a 3-D conceptual model was designed and simulated using the TOUGH2/EOS7C program. Simulation results show that CO2 injection can effectively enhance recovery of water-soluble gas. Sensitivity studies indicate that CO2 storage and energy production increase with the increases in well spacing and reservoir thickness. Numerical simulation was used to model the impact of factors such as reservoir heterogeneity and injection fluid on thermal energy recovery and CO2 storage. Simulation results show that the economic revenue per ton of CO2 storage under injecting fluid with the dissolved CO2 is approximately 18 times greater than that of injecting pure CO2. This revenue will offset the capture and storage costs of CO2 to a large extent. Considering the economics and the escape risk of carbon dioxide in aquifers, injecting fluid with the dissolved CO2 is the best injection method. The results of CO2-GWSGR technology provide new perspectives and valid technical references for geothermal-type water-soluble gas production and carbon dioxide storage.