Reservoir Scale Porosity-Permeability Evolution in Sandstone Due to CO2 Geological Storage

CO2 injection into geological reservoirs is considered as a promising technology to improve oil recovery from oil reservoirs and to reduce greenhouse gas emissions. However, due to the density difference between the injected CO2 and formation brine, the injected CO2 tends to move vertically towards the surface. The risk of this vertical CO2 movement can be prevented by four different trapping mechanisms (i.e. structural, residual, dissolution, and mineral trapping). From the dissolution of CO2 in the aquifer brine, carbonic acid will be formed. Then, this carbonic acid will be reacted with rock minerals and resulted in mineral dissolution and precipitation. However, the effect of these mineral interactions on the porosity-permeability evolution during the CO2 storage process in the sandstone reservoir has not been addressed effectively. Thus, here, we developed a 3D reservoir simulation model to investigate the effect of mineral interactions on the reservoir porosity and permeability during CO2 injection and storage processes in a sandstone reservoir. The multicomponent, chemically reactive, non-isothermal and multiphase flow numerical simulation program TOUGHREACT has been used. The model length was 1000 m, model width was 1000 m and the model thickness was 1000 m (ranging from top depth of 1000 m and bottom depth of 2000 m) with a regularly spaced grid of 15 × 15 × 48 grid (10800 gridblocks). The developed reservoir simulation model consists of two main regions which are reservoir rock region (sandstone) and cap rock region (shale). The simulated sandstone formation consists of quartz, kaolinite, chlorite, and illite. Our results show that CO2 injection leads to significant mineral reactionس (dissolution and precipitation) in the sandstone reservoir. Furthermore, the results indicate that these mineral reactions lead to increase in the sandstone porosity and permeability during the storage period. Thus, we conclude that the mineral reactions (dissolution and precipitation) due to CO2 injection in the sandstone reservoir affect the sandstone porosity and permeability, and hence, affect the CO2 geological storage capacity.