Study on the Microscopic Mobilization Mechanism of CO2 Injection into High Water-Cut Deep Reservoir: Microfluidic and Lattice Boltzmann

CO2 injection into deep reservoirs is expected to be an efficient method to enhance oil recovery (EOR) and CO2 utilization and storage (CUS). However, the basic understanding of the interaction characteristics and miscible behavior of oil–water–CO2 fluids under high temperature and high pressure is mainly limited to traditional microfluidic techniques and pore-scale simulation methods. In this study, the dynamic miscible flow behavior of crude oil and supercritical CO2 in porous media was found through the microfluidic experiment of CO2 injection after water flooding at 55 MPa and 115 °C. Based on the experimental observations, a lattice Boltzmann model for oil–water–CO2 multiphase flow has been established. The model matches the experimental results, and the oil–CO2 miscibility behavior and the displacement efficiency can be accurately described. The results show that, compared with conventional reservoir, CO2 flooding in deep reservoir can better utilize the dead zone oil with the help of miscibility. At the same time, mixing with CO2 to reduce the viscosity of crude oil can be faster through the narrow throat. However, in practical application, although high CO2 injection rate can quickly recover oil, it may affect the overall recovery rate and reduce CO2 utilization efficiency.