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为深化研究已开发低渗油藏注气提高采收率机理,优化注气方式,通过采用长岩心物理模拟实验,考察油藏在目前地层压力条件下连续注CO_2驱、连续注N2驱、CO_2前段塞+N_2后续驱等不同注入方式下的气驱驱油效果。研究表明,N_2助推CO_2方式可有效提高原油采收率,实验产出关系曲线呈现“S”形态,分为3个阶段,采出程度的大幅增加主要发生在注气开发开采的第一阶段,对于衰竭开采后的注气实验,连续注CO_2驱、0.41HCPVCO_2前段塞+N_2后段塞的总采收率几乎相当,都超过了80%,因此采用N_2助推,如果CO_2段塞体积选择适当,其效果完全不逊于连续CO_2驱,而且降低了CO_2使用量,另N_2制备和运输整个流程中风险都较小,即使出现气体泄漏,也不会对环境造成太大伤害和影响,经济效益大幅提高。该研究成果将为低成本高效动用已开发低渗油藏提供技术支撑。
In order to deepen the research on the mechanism of enhanced gas recovery and recovery of oil in gas reservoirs with low permeability and to optimize the method of gas injection, a long-core physical simulation experiment was conducted to investigate the effects of continuous injection of CO2 flooding, continuous N2 flooding and CO2 The first section of the plug + N_2 follow-up flooding and other different modes of injection drive flooding effect. The results show that the N_2 boost CO_2 mode can effectively enhance the recovery rate of crude oil. The experimental output curve shows “S” shape and is divided into three stages. The significant increase of recovery degree mainly occurs in the In the first stage, for the gas injection experiment after depletion exploitation, the continuous recovery of CO_2 flooding and the recovery of 0.41HCPVCO_2 front slug + N_2 rear slug are almost the same, all exceeding 80%. Therefore, The volume is properly selected, the effect is not worse than continuous CO_2 flooding, and reduce the amount of CO_2, while the other N_2 preparation and transportation of the entire process are less risky, even if the gas leak, it will not cause much harm and impact on the environment, Significant increase in economic efficiency. The research results will provide technical support for the low cost and high utilization of developed low permeability reservoirs.