挥发性油藏CO2驱动态混相特征  

Dynamic miscibility characteristics of CO2 flooding in volatile oil reservoirs

作　　者：王锐[1] 吕成远[1] 伦增珉[1] 王进安 赵淑霞[1] 王欣[1] 许寻 WANG Rui;LÜChengyuan;LUN Zengmin;WANG Jin’an;ZHAO Shuxia;WANG Xin;XU Xun(Petroleum Exploration&Production Research Institute,SINOPEC,Beijing City,100083,China;Exploration&Production Research Institute,Zhongyuan Branch Company,SINOPEC,Puyang City,Henan Province,457000,China)

机构地区：[1]中国石化石油勘探开发研究院,北京100083 [2]中国石化中原油田分公司勘探开发研究院,河南濮阳457000

出　　处：《油气地质与采收率》2020年第1期89-92,共4页Petroleum Geology and Recovery Efficiency

基　　金：国家重点研发项目“致密油藏CO_2驱多相多组分流动机理及CCUS集成优化分析”（2016YFB0600805-1）;国家自然科学基金青年基金项目“富CO_2流体作用下储层和盖层溶蚀及充填作用机理——以黄桥富CO_2油气藏为例”（41602160）

摘　　要：挥发性油藏地层能量充足,原始地层压力高,常规水驱开发难以实施。CO2驱以其良好的驱油特性在该类油藏中得到了应用,但由于挥发性原油气油比高,溶解气中甲烷含量高,导致CO2驱混相压力高,使得其驱油效果受到一定的影响。通过室内实验和数值模拟,研究挥发性油藏注CO2过程中的动态混相特征,并剖析衰竭开发转CO2驱界限。结果表明:挥发性油藏存在着适度衰竭转CO2驱"脱气降混"机理,即随着地层压力的降低,原油中甲烷成分部分脱出,有助于CO2驱最小混相压力的降低。另外,其脱气降混程度与其原油类型和溶解气油比有关,原油越接近于凝析油,气油比越高,混相压力降低程度越大;反之,原油越接近于黑油,气油比越低,混相压力降低程度越小。结合动态混相机理,提出了挥发性油藏衰竭开发转CO2驱界限,即气油比越高,其转驱界限越低,脱气后CO2混相驱补充地层能量幅度越小;反之,转驱界限越高,补充地层能量幅度越大。It is difficult to carry out water flooding in volatile oil reservoirs due to the sufficient formation energy and the high initial pressure. CO2 flooding has been implemented in this type of reservoir for its excellent oil displacement characteristics. However,the higher dissolved gas oil ratio and the higher methane content contribute to a higher minimum miscible pressure(MMP)of CO2 flooding,which decreases the displacement performance. Dynamic miscibility characteristics and the injection timing of CO2 injection for volatile oil reservoirs are studied through laboratory experiment and numerical simulation. The results show that the characteristics of releasing methane and decreasing CO2 MMP is evident in the CO2 flooding after a depletion production of volatile oil reservoirs. That is to say,methane partially releases from the crude oil as the formation pressure decreases,which is favorable to the decreasing of CO2 MMP. The extent of decreasing CO2 MMP is closely related to the crude oil type and initial dissolved gas-oil ratio. When the crude oil is closer to the condensate oil,a higher dissolved gas-oil ratio results in a lager decreasing degree of MMP. On the contrary,when the crude oil is closer to black oil,a lower dissolved gas-oil ratio results in a smaller degreasing degree of MMP. The CO2 injection timing after the depletion of volatile oil reservoirs is proposed according to the dynamic miscibility mechanism. It is found that as the dissolved gas-oil ratio increases,the injection timing and the formation energy supplement decrease. Otherwise,the injection timing and the formation energy supplement increase.

关 键 词：挥发性油藏 CO2驱 脱气降混 转驱界限 混相压力 

分 类 号：TE357.45[石油与天然气工程—油气田开发工程]