CO2 storage capacity estimation by considering CO2 Dissolution: A case study in a depleted gas Reservoir, China

Accurate evaluation of CO2 storage potential in depleted gas reservoirs especially considering the CO2 dissolution in formation water is still challenging. This work develops an analytical model to calculate the CO2 storage capacity considering its dissolution in formation water based on the principle of molar balance. The dissolved gas-water ratio (GWR) is calculated by CSMGem. The impact of formation temperature, pressure, fluid composition on the dissolved GWR and CO2 storage capacity is analyzed. The CO2 storage volume of two wells in the CS gas reservoir are evaluated based on the proposed model. Results show that the CO2 storage volume of Well #L1 and Well #L2 are significantly increased by 1.15 and 1.43 times after considering CO2 dissolution. Thus, the dissolved CO2 storage volume cannot be ignored. The CH4-rich gas reservoirs with shallow-medium depth are preferred for CO2 storage based on the dissolved GWR analysis, but the safety, injection ability and operation costs need be considered. This work also provides a reference for CO2 storage potential prediction in underground porous media with formation water.