The characteristics of CO2 front dynamic migration in low permeability sandstone oil reservoirs under different miscibility degrees

CO2 flooding is a significant technology for oil recovery, to reveal the microcosmic mechanism of CO2 flooding, CO2 slim tube experiments, long core CO2 flooding experiments, gas chromatography analysis experiments, and numerical simulations were carried out. The results show that the miscibility increase can improve the effect of dissolution and diffusion in the CO2-crude oil system, easing the CO2 finger entry phenomena, and delaying gas breakthrough time. Besides, the CO2 -crude oil interaction is enhanced by increasing the pressure difference between the injection well and the production well, which improves the oil recovery of CO2 flooding. Besides, CO2 carries the light and medium components (C4 ~ 25) forward to cross the first miscible zone, which makes the CO2-crude oil system form double miscible zones. This study reveals the rule of CO2 front and light components front under different miscibility degrees of CO2 flooding from the microscopic perspective and deepens the theory of CO2 flooding in low-permeability sandstone reservoirs.