Numerical simulation of CO2-brine-rock interactions on CO2 sequestration in Shihezi Formation of Ordos Basin in China

Carbon Capture and Storage (CCS), as the best way of reducing carbon emissions under existing technological conditions, is attracting more and more attention. Although experiments can explore chemical process of CO2 sequestration, it is limited in time scale. CO2 geological storage will last hundreds and thousands of years, so TOUGHREACT is used to conduct kinetic batch modeling and reactive transport modeling. In this paper, CO2-water-rock interaction mechanisms and theirs effects on reservoir are discussed in detail, especially on how pore structure and properties are changing. The first CCS project in China is carried out in Ordos basin. Geochemical simulation tool TOUGHREACT is used to simulate CO2-water-rock interactions at Shihezi formation in Ordos basin. Geochemical reactions play an important role in CO2 geological storage environments, because they may change the properties of reservoir. Although CO2-water-rock interaction rate may be very small, it is an ideal way of CO2 geological storage. No matter what minerals dissolve and precipitate, they will enhance the dissolution of CO2. For long-term storage, CO2-water-rock interaction can promote amount of CO2 mineralization referred to as mineral trapping, which has a positive effect on the feasibility of CO2 storage.