Mineralization Reaction Behavior during CO₂ Flooding in Reservoirs

CO2 flooding is a promising technology for enhancing oil recovery while achieving geological CO2 storage. Under high‑temperature and high‑pressure reservoir conditions, CO2 dissolves in formation water to form carbonic acid, which reacts chemically with the reservoir rock minerals to achieve safe CO2 storage. Currently research on mineralization reactions during CO2 flooding in oil reservoirs remains limited, the characteristics of such reactions under different conditions and their impact on rock physical properties are not well understood. This study conducted static dissolution experiments to investigate the effects of various factors such as reservoir temperature, pressure, salinity, and oil saturation on the reaction behavior of the CO2-crude oil-water-rock system. The results indicate that CO2 dissolved in water can dissolve minerals such as calcite in the rock samples, leading to increased porosity and permeability. Although higher temperature promotes mineralization reactions, it also reduces the solubility of CO2 in water, resulting in an overall weakening of reaction intensity. As reservoir pressure rises or formation water salinity decreases, the extent of mineralization intensifies and the rock dissolution rate increases. However, the presence of crude oil inhibits the mineralization reaction between CO2 and rock, increasing oil saturation from 20% to 70% reduced the mineral dissolution rate by roughly 94% (from 3.77% to 0.22%), indicating a significant shielding effect.