Dong Yuanwu, Hu Hao, Wang Rui, Wang Siyao, Meng Wenyu, Chen Zequn, Tang Shanfa
School of Petroleum Engineering, Yangtze University, Wuhan, Hubei430100, China.
Hubei Key Laboratory of Oil and Gas Drilling Engineering, Wuhan, Hubei430100, China.
ACS Omega. 2023 Feb 2;8(6):5625-5633. doi: 10.1021/acsomega.2c07109. eCollection 2023 Feb 14.
CO flooding is an important technology to enhance oil recovery and realize effective storage of CO in ultra-low permeability reservoir. However, due to poor reservoir properties, strong interlayer heterogeneity, and unfavorable mobility ratio of CO, gas channeling easily occurs, resulting in low recovery. Chemically assisted CO thickening technology has been developed to control the gas flow rate and improve the CO repulsion effect. Through solubility and viscosity enhancement tests, the CO viscosity enhancer composite system is preferably constructed and then combined with the core drive experiments, the effect of CO viscosity enhancer composite system on oil drive in homogeneous and non-homogeneous cores is evaluated, the correlation between the drive efficiency and viscosity enhancement and solubility of the system is analyzed, and the mechanism of recovery enhancement is explored. The results show that the preferably constructed CO-ASA-LAP composite system has a good effect for improving the gas drive effect under simulated formation conditions, and its improvement effect is positively related to the solubility and viscosity increase of the system. Combining oil repelling efficiency and economic considerations, ASA:LAP = 1:1 is selected as the optimal CO viscosity enhancer composite oil repelling system. For homogeneous cores, the CO-ASA-LAP combined system drive can increase the recovery rate by 6.65% as compared with CO flooding. For heterogeneous cores, when the permeability difference is 5, the comprehensive recovery factor of the CO-ASA-LAP system flooding is 8.14% higher than that of CO flooding. When the permeability difference increases from 5 to 10, the comprehensive recovery factor of the CO-ASA-LAP system flooding increases by 1.85%.The injection of the CO-ASA-LAP system has some injurious effect on the permeability of the reservoir core, and the smaller the permeability, the greater the degree of injury. The mechanism of the CO-ASA-LAP system to improve recovery includes increasing CO viscosity, improving the oil repelling flow ratio, blocking high seepage channels, initiating low seepage residual oil, enhancing CO dissolution, and expanding the oil repelling effect.
二氧化碳驱油是提高原油采收率和实现二氧化碳在超低渗透油藏有效封存的一项重要技术。然而，由于油藏物性差、层间非均质性强以及二氧化碳驱替流度比不利，容易发生气窜，导致采收率较低。为此开展了化学辅助二氧化碳增稠技术研究，以控制气体流速，提高二氧化碳驱替效果。通过溶解度和黏度增强试验，优选构建了二氧化碳黏度增强复合体系，再结合岩心驱替实验，评价了二氧化碳黏度增强复合体系在均质和非均质岩心中的驱油效果，分析了驱替效率与体系黏度增强及溶解度之间的相关性，探索了采收率提高的机理。结果表明，优选构建的二氧化碳-ASA-LAP复合体系在模拟地层条件下对改善气驱效果具有良好作用，其改善效果与体系的溶解度和黏度增加呈正相关。综合驱油效率和经济因素考虑，选择ASA:LAP = 1:1作为最佳的二氧化碳黏度增强复合驱油体系。对于均质岩心，二氧化碳-ASA-LAP复合体系驱替与二氧化碳驱相比，采收率可提高6.65%。对于非均质岩心，渗透率级差为5时，二氧化碳-ASA-LAP体系驱替的综合采收率比二氧化碳驱高8.14%。当渗透率级差从5增大到10时，二氧化碳-ASA-LAP体系驱替的综合采收率提高了1.85%。注入二氧化碳-ASA-LAP体系对油藏岩心渗透率有一定伤害作用，渗透率越小，伤害程度越大。二氧化碳-ASA-LAP体系提高采收率的机理包括增加二氧化碳黏度、提高驱替流度比、封堵高渗通道、启动低渗残余油、增强二氧化碳溶解以及扩大驱油效果。
