Numerical simulation of CO2 storage by basalts in Xingouzui formation, Jianghan Basin, China

Sedimentary basins often develop large amounts of basalts, but there are few studies. The diagenetic history of basalts in sedimentary basins is different from that of continental flood basalts and deep-sea basalts. A large amount of basalt is developed in the Jianghan Basin. Minerals undergo varying degrees of alteration, such as the alteration of olivine into serpentine. Numerical simulations were used to study the interaction between basalt-CO2-formation water in the Xingouzui Formation. The effects of basalt alteration and CO2 injection mode (supercritical CO2, saturated CO2 water, co-injection of CO2 and water) on CO2 storage were investigated. The results show that the reactivity between unaltered basalt and CO2 is strong, and the maximum CO2 mineral trapping reaches 22–49 kg/m3 after CO2 injection for one month. However, the reactivity between the altered basalt and CO2 is obviously decreased. Compared with the unaltered basalt, the maximum CO2 mineral trapping for the altered basalt decreased by at least 15.4 % after CO2 injection for one year. For severely altered basalt with high serpentine content, the maximum CO2 mineral trapping even drops by more than 90 %. CO2 mineral trapping will be overestimated when the feedback of reservoir porosity and permeability changes on flow is not considered. The co-injection of CO2 and water can make full use of the advantages that water injection can promote CO2 dissolution and the resulting acidic environment is beneficial to mineral dissolution. This method could be an option after careful assessment of CO2 leakage risks and technical feasibility.