Reactive Transport Modeling of CO2-Brine-Rock Interaction on Long-Term CO2 Sequestration in Shihezi Formation

Carbon Capture and Storage (CCS) is attracting increasing scientific attention. Although experiments can explore the chemical process of CO2 sequestration, they are limited in time. CO2 geological storage will last hundreds and thousands of years, even much longer, so the numerical simulation method is used to conduct kinetic batch modeling and reactive transport modeling. The geochemical simulation tool-TOUGHREACT-is used to imitate CO2-brine-rock interactions at the Shihezi Formation in the Ordos basin. The mechanisms of CO2-brine-rock interaction and their effects on the reservoir are discussed, especially the change in structure and properties. K-feldspar and albite will dissolve as the main primary minerals. However, calcite and quartz will dissolve first and precipitate last. In addition, siderite and ankerite also appear as precipitation minerals. Mineral dissolution and precipitation will alter the formation of petrophysical parameters, such as porosity and permeability, which play significant roles in the geological storage environments. Although the CO2-brine-rock interaction rate may be small, it is an ideal way of geological storage. Regardless of what minerals dissolve and precipitate, they will improve the dissolution of CO2. The interaction between rock and brine with dissolved CO2 can promote the amount of mineralization of CO2, called mineral trapping, which has a positive effect on the long-term feasibility of CO2 storage.