致密油藏超临界二氧化碳吞吐开发特征实验研究

针对鄂尔多斯盆地致密油藏采油速度快速递减、油藏压力无法保持的问题,探索采用超临界CO₂吞吐开发方式开展超临界CO₂吞吐长岩心实验研究,探讨了超临界CO₂吞吐方式提高致密油采收率的作用机理、开发特征、影响因素等,探究了注气速度、注气相态、N₂辅助保压、衰竭压力等重要操作参数对提高致密油采收率的影响。研究表明:超临界CO₂吞吐能有效提高致密油采收率,效果优于常规CO₂吞吐;注气速度对采收率影响较小;注N₂辅助保压能大幅度提高致密油采收率及换油率;吞吐前3个周期开发效果最佳,占总采收率的91.5%。研究成果证实了注超临界CO₂吞吐提高致密油采收率的可行性及巨大应用潜力,可为鄂尔多斯盆地致密油藏高效开发提供理论基础和技术支持。

Experimental Study on Development Characteristics of Supercritical CO2 Huff and Puff in Tight Oil Reservoirs

In view of the rapid decline in oil recovery rate in tight oil reservoirs of the Ordos Basin and the inability to maintain reservoir pressure, the development method with CO₂ huff and puff was discussed, and the experimental study on supercritical CO₂ huff and puff with long core was carried out. The mechanism, development characteristics and influencing factors of supercritical CO₂ huff and puff in enhancing tight oil recovery were explored. The influence of key operating parameters, such as gas injection rate, gas injection phase, pressure holding with N₂, and depletion pressure, on tight oil recovery was discussed. The study shows that: supercritical CO₂ huff and puff can effectively improve tight oil recovery, with effect better than conventional CO₂ huff and puff. Gas injection rate has little effect on oil recovery. Injection N₂ to hold pressure can significantly improve tight oil recovery and oil exchange rage. The first three cycles of huff and puff are of best effect, accounting for 91.5% of the total oil recovery. The research result confirmed the feasibility and huge application potential of supercritical CO₂ huff and puff in improving tight oil recovery, and can provide theoretical basis and technical support for the efficient development of tight oil reservoirs in the Ordos Basin.