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低渗透油藏渗透率对CO2驱重力超覆的影响规律
宋黎光,赵凤兰,冯海如,王强,娄小康
0
(1.中国石油大学(北京)非常规油气科学技术研究院,北京102249;2.石油工程教育部重点实验室,北京102249;3.中国石油大学(北京)石油工程学院,北京102249)
摘要:
为明确低渗透油藏渗透率对CO2驱重力超覆的影响规律及相关机理,采用气驱超覆物理模型开展不同渗透率岩心的CO2非混相和混相驱室内实验,以岩心气体突破时的上层采收率所占比重及岩心最终采收率等参数评价重力超覆程度,从而得出重力超覆规律,并分析其影响机理。实验结果表明,在较小渗透率变化范围内,渗透率增加对黏性力及重力的增加幅度影响较小,尤其在混相驱中,油气黏度和密度差异较小,渗透率增大后重力超覆的程度增加不明显;渗透率增加将增大非混相驱中气驱前缘移动速度,降低混相驱中油气混相程度,加之重力超覆程度加剧,最终采收率较低;韵律油层开发中可利用渗透率对重力超覆的影响规律,避免或利用重力超覆,尤其在CO2非混相驱中,正韵律油层的开发效果会更好。
关键词:  低渗透油藏  渗透率  CO2驱  重力超覆  影响规律
DOI:10.13673/j.cnki.cn37-1359/te.2020.04.013
基金项目:国家科技重大专项“ 低渗-致密油藏高效提高采收率技术”(2017ZX05009-004)和“ 海外重点油气田开发钻采关键技术”(2017ZX05032-004)。
Influence of permeability on gravity segregation during CO2 flooding in low-permeability reservoirs
SONG Liguang,ZHAO Fenglan,FENG Hairu,WANG Qiang,LOU Xiaokang
(1.Unconventional Oil and Gas Institute,China University of Petroleum(Beijing),Beijing City,102249,China;2.Key Laboratory of Petroleum Engineering of the Ministry of Education,Beijing City,102249,China;3.College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing City,102249,China)
Abstract:
In order to clarify the effect of permeability on gravity segregation and related mechanisms during CO2 flooding in low-permeability reservoirs,the CO2 immiscible and miscible flooding experiments on cores with different permeability are carried out according to gas gravity segregation model,and the recovery of top layer at gas breakthrough and final recovery are used to evaluate gravity segregation level and to reveal its mechanism. The results indicate that within a small permeability variation range,the increase of permeability has little effect on the increase of the viscosity and gravity,especially in miscible flooding,the viscosity and density difference of oil and gas are small,the increase of gravity segregation is not obvious after the permeability increase;the increase of permeability also increases the moving velocity of gas front and decreases the miscibility of oil and gas in immsicible flooding test,which produces a low final recovery with the influence of gravity segregation. The variation of gravity segregation with permeability can be applied to the production of rhythmic reservoirs to avoid or use the gravity segregation,especially in immiscible flooding,CO2 flooding performance in positive rhythm reservoirs could be better under the gravity segregation.
Key words:  low-permeability reservoirs  permeability  CO2 flooding  gravity segregation  influence law

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