Mechanisms of Fluid Migration and CO2 Storage in Low Permeability Heavy Oil Reservoirs Using High-Pressure Microfluidic CO2 Flooding Experiment

The effective development of low permeability heavy oil reservoirs is crucial for tapping into unconventional resources. High-pressure CO2 flooding offers numerous benefits, including reducing crude oil viscosity, enhancing oil fluidity, and decreasing interfacial tension, leading to improved heavy oil production. Additionally, CO2 can be sequestered in the formation, contributing to carbon emission reduction. However, analyzing the migration and storage effects of CO2 in low permeability heavy oil reservoirs is challenging. In this study, high-pressure and high-temperature (50 MPa,100 °C) microfluidic experiments were designed and carried out, and the CO2 flooding characteristics and storage efficiency were studied. The distribution of the remaining oil and mechanisms of CO2 sequestration under various displacement speeds and injection pressures were analyzed. The results demonstrated that CO2 flooding achieved significantly higher recovery rates compared to high-pressure water flooding, with increments of 13.89, 21.53, and 23.09% at oil displacement pressures of 30, 40, and 50 MPa, respectively. The CO2 burial efficiency also showed substantial improvements, reaching 23.55, 34.01, and 37.13% under the corresponding conditions. Furthermore, a higher porosity facilitated CO2 migration, providing more space and migration channels for CO2 flow. By examining CO2–oil interactions, the study elucidated CO2 migration patterns and burial efficiency under different displacement modes.