Numerical Simulation on Interaction Between the Supercritical CO2 and Water-Rock in Tarim Basin

Abstract

Abstract Climate change is related to human survival and long-term development. In the context of global carbon neutrality, carbon dioxide capture, utilization, and storage play a key role in carbon emission reduction. Supercritical CO2 appears weakly acidic when dissolved in water. After contact with the reservoir, the carbonate rock in formation will react with the CO2 aqueous solution, which will lead to the process of original mineral dissolution and secondary mineral precipitation, and affect the seepage process. The numerical simulation method is used to study the CO2-water-rock reaction time and storage capacity in structural and stratigraphic trapping, residual trapping, solubility trapping, and mineral trapping. Solubility trapping utilizes CO2 to dissolve in the aqueous phase at a certain pressure/temperature to achieve the purpose of storage. It largely depends on pressure, temperature, and surface area in contact with water bodies. Residual trapping uses the effect of the relative permeability curve from displacement to suction to trap the non-wetting phase. The mineral trapping of Anorthite, Calcite, and Kaolinite after CO2 injection under the initial condition of PH=7 was simulated. Comparison of water-rock reactions under four different storage methods. The results show that, during the simulation process, anorthite gradually dissolved, kaolinite gradually precipitated, and calcite initially dissolved and then precipitated. In the early stage of CO2 injection and reaction, more than 90% of CO2 is stored by structural and stratigraphic trapping and residual trapping, and there is a small amount of solubility trapping. The contribution rate of mineral trapping is about 0. With time, the amount of CO2 stored by solubility trapping and mineral trapping gradually increases, the concentration of CO2 dissolved in formation water and the concentration of Ca2+ and Mg2+ increase significantly, the dissolution rate of formation rock increases, and the mineral trapping rate of CO2 also increases. It will take decades or even hundreds of years to realize the permanent storage of CO2. This provides theoretical support for long-term and safe storage of CO2 in reservoirs and prediction of storage methods and has certain guiding significance.