摘要
Water alternating gas(WAG)injection is a widely used strategy for enhancing oil recovery(EOR)during gas flooding,and the mechanisms,operating parameters,and influencing factors of which have been extensively studied.However,with respect to its capacity in expanding macroscopic sweep volume under varying heterogeneities,the related results appear inadequate.In this research,three cores with different heterogeneities were used and flooded by the joint water and CO_(2) WAG,then the effects of heterogeneity on oil recovery were determined.More importantly,the cores after CO_(2) WAG injection were investigated using the nuclear magnetic resonance(NMR)technique for remaining oil distribution research,which could help us to understand the capacity of CO_(2) WAG in enlarging sweep volume at different heterogeneities.The results show that the presence of heterogeneity may largely weaken the effectiveness of water flooding,the more severe the heterogeneity,the worse the water flooding.The WAG injection of CO_(2) performs well in EOR after water flooding for all the cores with different heterogeneities;however,it could barely form a complete or full sweep throughout the low-permeability region,and un-swept bypassed regions remain.The homogeneous core is better developed by the injection of the joint water and CO_(2) WAG than the heterogeneous and fractured cases.
水气交替(WAG)是注气提高采收率(EOR)中应用较为广泛的注入方式,其主要驱油机理、参数优化和影响因素等已有较多的研究。然而,有关其在不同非均质性条件下扩大波及体积能力的报道不多。在三块非均质性不同的岩心模型中,依次开展了水驱和CO_(2)-WAG驱,研究了非均质性对WAG提高采收率的影响。更为关键的是,对CO_(2)-WAG注入后利用核磁共振技术(NMR)对模型中剩余油的分布进行扫描,能够对不同非均质性模型中CO_(2)-WAG驱扩大波及体积的效果有直观判断。结果表明,非均质性的出现会严重削弱水驱的有效性:非均质性越强,水驱效果越差。水驱后,CO_(2)-WAG驱在不同非均质性条件下均能较好地提高采收率,但是并不能对低渗区域形成完全的波及,驱替后仍然存在无法驱扫的区域。水驱和CO_(2)-WAG驱对均质岩心模型的开发效果较非均质模型好。
作者
WANG Ye-fei
LI Zong-yang
ZHANG Shi-ming
LIU De-xin
DING Ming-chen
王业飞;李宗阳;张世明;刘德新;丁名臣(Key Laboratory of Unconventional Oil&Gas Development,Ministry of Education,China University of Petroleum(East China),Qingdao 266580,China;Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil&Gas Reservoirs,Xi’an Shiyou University,Xi’an 710043,China;Shandong Key Laboratory of Oilfield Chemistry,China University of Petroleum(East China),Qingdao 266580,China;Exploration and Development Research Institute of Shengli Oilfield,Dongying 257100,China)
基金
Project(KFJJ-TZ-2019-3)supported by the Open Project of Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil&Gas Reservoirs,China
Projects(51504275,51974344)supported by the National Natural Science Foundation of China。
