Abstract
The effect of CO2 adsorption on oil displacement in tight reservoirs is analyzed. The composition of clay minerals in a reservoir is analyzed, and a molecular model of the formed rock structure is established to investigate the adsorption characteristics of different clay minerals on the fluid. The effect of CO2 adsorption on oil displacement is investigated through a CO2 injection experiment. The results show that the adsorption capacity of reservoir minerals is greater for light hydrocarbons than for heavy hydrocarbons as well as for water and CO2 than for hydrocarbons, indicating that the oil recovery rate of the reservoir composed primarily of silica is higher when supercritical CO2 and water are alternately injected. The oil recovery can reach 23.78% by water and CO2 alternate flooding. Intermittent stop injection enable CO2 to enter rock samples more easily, and crude oil can subsequently be discharged more easily. As the mixing of CO2 and crude oil cannot be realized under the experimental conditions, the intermittent stop injection time is short and the gravity migration in tight cores is slow. Hence, we infer that the adsorption of CO2 significantly affects the displacement of tight reservoirs.
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