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The effective development of low permeability heavy oil reservoirs is crucial for tapping into unconventional resources. High-pressure CO2flooding offers numerous benefits, including reducing crude oil viscosity, enhancing oil fluidity, and decreasing interfacial tension, leading to improved heavy oil production. Additionally, CO2can be sequestered in the formation, contributing to carbon emission reduction. However, analyzing the migration and storage effects of CO2in 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 CO2flooding characteristics and storage efficiency were studied. The distribution of the remaining oil and mechanisms of CO2sequestration under various displacement speeds and injection pressures were analyzed. The results demonstrated that CO2flooding 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 CO2burial efficiency also showed substantial improvements, reaching 23.55, 34.01, and 37.13% under the corresponding conditions. Furthermore, a higher porosity facilitated CO2migration, providing more space and migration channels for CO2flow. By examining CO2–oil interactions, the study elucidated CO2migration patterns and burial efficiency under different displacement modes.

Carbon utilization, and sequestration (CUS) in tight oil reservoirs stands as a pivotal strategy for enhancing oil recovery and mitigating CO2emissions. Research on CUS mainly focuses on the calculation of overall displacement efficiency and the total sequestration amount. However, the primary control and sequestration mechanisms throughout the life cycle of CUS, as well as the contribution of each mechanism at different development stages and under various injection and production parameters, are not clear, which limits effective guidance for oilfield development. Therefore, this paper studies the entire life cycle of tight oil reservoirs, from water flooding to CO2flooding and CO2sequestration after reservoir abandonment. The contribution degree changes of dissolution, structural, residual gas and mineralized sequestration mechanisms during the whole life cycle are analyzed. The results show that the main sequestration mechanism during CO2flooding stage and injection sequestration stage after shutting down production wells is structural sequestration, which accounts for 84.75%. In the 2000 years following the cessation of CO2injection, the proportion of structural sequestration gradually decreases, with a cumulative decrease of 12.41%, and it is mainly converted to the other three sequestration modes, with the largest increase in mineralization sequestration, reaching 8.81%, mainly due to the reaction of dicalcium silicate with CO2to produce more stable calcite. When the injection pressure was increased from 23 MPa to 44 MPa, the sequestration efficiency increased by 18.45%. An interesting finding is that the solubility of CO2in water in the target reservoir reaches its lowest point at 80 °C, and both warming and cooling at this point are conducive to the dissolution and sequestration of CO2. The initial pH value of formation water mainly affects mineralization and sequestration. The rate of calcite production and the contribution of CO2dissolution and sequestration are positively correlated with water saturation. The findings underscore the importance of understanding dynamic contributions of various sequestration mechanisms and optimizing conditions to enhance CO2sequestration efficiency.