Analysis of Factors Impacting CO2 Assisted Gravity Drainage in Oil Reservoirs with Bottom Water

Abstract

In recent years, there has been significant focus on the issue of global carbon emissions. One of the most prominent areas of research in this regard is the use of carbon capture, utilization, and storage (CCUS) technology in the petrochemical industry. At present, the utilization of CO2 Assisted Gravity Drainage (CAGD) in oil reservoirs, particularly those containing bottom water, is considered to be in the early stages of exploration and development. In this study, a mechanistic model was built, and five key factors influencing CAGD were analyzed. These factors included the reservoir structure, CO2 injection site, initial formation pressure, reservoir thickness, and CO2 injection rate. Then, the applicable rules governing CAGD in oil reservoirs with bottom water were obtained. Finally, these rules were employed in an actual reservoir to optimize the injection-production parameters. The results of the influence factor analysis indicated that CAGD was more suitable for anticline structural reservoirs. The combined top-waist CO2 injection could fully utilize gravity differentiation in a short timeframe to expand the lateral sweep range of the CO2. CAGD was more effective when the reservoir pressure was greater than the minimum miscible pressure and the reservoir thickness was between 25–50 m. The generation of a secondary CO2 cap was favored when the CO2 injection rate was 35,000 m3/d. Results from A Oilfield applications indicated that, following the application of CAGD technology, A Oilfield experienced an increase in cumulative oil production of 15.76 × 104 t, a 10% reduction in water cut, and an amount of 82.15 × 106 m3 of CO2 that was sequestered in the subsurface. These findings can offer practical insights and guidance for the future development of CAGD techniques in similar reservoirs.