An experimental investigation of inorganic sediment damage for CO2 flooding reservoirs

Carbon dioxide (CO₂) flooding is a technology for improving the oil recovery of low-permeability reservoirs. However, the interaction between CO₂-water induced by CO₂ injection can lead to the formation of inorganic sediments in reservoir pores, which seriously affects the effectiveness of CO₂ flooding. Therefore, experiments of CO₂-saltwater-rock reaction in a high-temperature and high-pressure reactor, and CO₂ flooding saltwater-saturated core samples were conducted to research the damage law of the reservoir due to the formation of inorganic sediments. We found that the inorganic precipitation formed in reservoir pores with CO₂ flooding is mainly siderite and kaolinite, and the number of sediments increases with the rise of contact pressure and temperature between CO₂ and saltwater. However, the precipitation in reservoir pores tends to dissolve when the contact pressure exceeds 40 MPa. The peak particle size of solid particles in the formation water is 1718 nm, which indicates the small pores below this pore size in the reservoir will be blocked during CO₂ flooding. To prevent the blockage impact of inorganic sediments, CO₂ injection pressure can be appropriately increased to promote precipitation dissolution.