Analyzing and Understanding the Influencing Factors of CO₂ Flooding in the Subei Complex Fault Block Reservoirs

The performance of CO₂ flooding in the complex fault block reservoirs of the Subei Basin varies greatly. In order to find effective measures to improve the development of these unique fault-block reservoirs, the main influencing factors were analyzed. Based on the data from 9 CO₂ flooding blocks in north Jiangsu, the influences of well type, fracturing conditions, initial production before gas injection, the injection-production ratio and the gas injection method on CO₂ flooding effects were analyzed. The analysis results show that the development effect of vertical wells is better than that of horizontal wells, and it is better for non-fractured wells than fractured. The higher the initial production of the well, the better the CO₂ flooding effect. The optimal injection-production ratio is around 2.5, while CO₂ injection methods play an insignificant role in the development effect. The results show that those factors, such as low permeability reservoir well type and the necessity of reservoir stimulation, are the main factors influencing CO₂ flooding. Those issues need to be fully considered in improving the CO₂ flooding effect in the complex fault block reservoirs in the Subei Basin.