二氧化碳驱含气上升规律及气窜综合治理方法

On gas rising law of CO_(2) flooding and gas channeling comprehensive treatment method

气窜是影响二氧化碳(CO_(2))驱实施效果的关键因素。中原油田多数实施CO_(2)驱的区块已发生不同程度气窜,严重影响油田后期的开发效果。针对气窜导致的CO_(2)驱实施效果变差等问题,开展了含气上升规律及气窜综合治理研究。以室内CO_(2)驱替实验为基础,明确了非混相驱CO_(2)突破时间早于混相驱,且驱替压力越高,突破时间越晚,最终采收率与混相驱结果越接近。采用油藏工程方法并结合现场实施情况分析,明确了中原油田CO_(2)驱含气上升主要呈现“凸型”与“S型”2种模式,“S型”含气上升模式多见于混相驱,“凸型”含气上升模式多见于非混相驱。针对不同类型油藏气窜模式,开展气窜综合治理方法研究,提出气窜治理以早期焖井恢复地层压力及优化注气方式等防治为主,后期工艺封窜为辅的综合治理方法。研究成果现场应用后提高CO_(2)驱采收率4.6%,为同类气藏提高CO_(2)驱开发效果提供借鉴。

Gas channeling is the key factor affecting the effect of CO_(2) flooding.At present,gas channeling has occurred to dif-ferent degrees in most of the CO_(2) flooding blocks in Zhongyuan Oilfield,which seriously affects the development effect of the oilfield in the later stage.Aiming at the problems such as the poor effect of CO_(2) flooding caused by gas channeling,the gas rise law and the comprehensive control of gas channeling are studied.Based on the CO_(2) displacement experiment in the laboratory,the results show that the CO_(2) breakthrough time of immiscible flooding is earlier than that of miscible flooding,and the higher the displacement pressure,the later the breakthrough time,and the closer the final recovery rate is to that of miscible flooding.Com-bined the reservoir engineering method and the analysis of the field implementation,which shown that the CO_(2) flooding gas rise in Zhongyuan Oilfield mainly presents“convex-type”and“S-type”modes,among which“S-type”gas rise mode is mostly oc-curred in miscible flooding,and“convex-type”gas rise mode is mostly occurred in immiscible flooding.According to the gas channeling mode of different types of reservoirs,the comprehensive treatment method of gas channeling was studied,which pro-posed that gas channeling should be prevented and controlled mainly by restoring formation pressure and optimizing gas injection mode in the early stage,and supplemented by sealing channeling in the later stage.The research results can increase the CO_(2) flooding recovery rate by 4.6%after field application,and provide reference for similar gas reservoirs to improve the CO_(2) flood-ing development effect.