Discontinuity Stability Analysis for Carbon Dioxide Enhanced Oil Recovery

Carbon dioxide (CO₂) enhanced oil recovery (EOR) is considered to be an effective measure to increase oil productivity by injecting CO₂ into reservoirs. Nevertheless, the injection of CO₂ can potentially induce instability in discontinuities such as faults and fractures within the reservoir, influencing the safety and efficiency of the operation. Qualitative analysis of fault stability was implemented in the integrated process of CO₂-EOR, by integrating fluid dynamics models, in-situ stress conditions and rock mechanics parameters. The results show that there is a pressure decreasing region around the oil producer, and CO₂ injection has a prominent influence on reservoir pressure maintenance. The reservoir pressure and liquid flow of oil producer is slightly higher from the beginning of CO₂ injection. The minimum effective normal stress and the maximum slip tolerance of the faults are aligned with the axis between the CO₂ injector and the oil producer. The fault friction angle is the primary factor in discontinuity stability analysis, influencing the slip rate and mode during CO₂-EOR. The larger the friction angle, the fewer faults are in the critical slip state. Fault stability analysis is a complete assessment, indicating that a fault may remain stable even if certain parts reach a critical state.