水相渗吸对页岩储层的物化作用机理研究  

Physicochemical mechanism of water phase imbibition in shale reservoirs

作　　者：李颖[1] 李茂茂 李海涛[1] 于皓 张启辉 罗红文 LI Ying;LI Maomao;LI Haitao;YU Hao;ZHANG Qihui;LUO Hongwen(Southwestern Petroleum University,Chengdu,Sichuan 610500,China)

机构地区：[1]西南石油大学,四川成都610500

出　　处：《油气藏评价与开发》2023年第1期64-73,共10页Petroleum Reservoir Evaluation and Development

基　　金：国家自然科学基金面上项目“SNPs提升CO_(2)地质封存泥岩盖层封堵能力的作用机制研究”(42272176);国家自然科学基金中国博士后科学基金“开发中后期页岩气藏多尺度输运机理研究”(309811)。

摘　　要：页岩气藏储层发育微纳米孔喉和裂缝,黏土矿物含量高,岩石渗透率低且非均质性较强,通常需要经过大规模水力压裂才能被有效开采。水力压裂过程中水相的自发渗吸将对页岩气藏储层产生一系列物化作用,改变页岩气藏储层的孔隙结构及物化性质,从而影响页岩气的产出。为进一步明确水相渗吸对页岩气藏储层的影响机理,开展了页岩重复渗吸对照实验,并基于页岩渗吸前后矿物溶蚀导致的质量变化、扫描电镜可视化特征、核磁共振孔隙结构观测以及物性的变化,揭示渗吸对页岩微观孔隙结构及其物性的影响机理。研究结果表明:(1)水相渗吸作用使页岩产生微裂缝和裂缝,从而改变页岩孔隙结构;(2)孔隙度明显改善的页岩样品中,大孔所占比例上升,表明水相渗吸作用会使页岩孔隙空间增大;(3)渗吸能力与页岩的孔隙度、渗透率呈正相关,且页岩物性在渗吸后改善明显。此外,发现时间指数可定量表征渗吸对页岩孔喉连通性的影响。Shale gas reservoirs,which develope micro-nano pore throats and fractures,have high clay mineral content,and strong heterogeneity of porosity.Therefore,large-scale hydraulic fracturing is usually needed to realize the effective exploitation.In the process of hydraulic fracturing,the spontaneous imbibition of the water phase will trigger a series of physical and chemical effects on the shale gas reservoir,changing the pore structures,physical and chemical properties of shale gas reservoirs,thereby affecting the production of shale gas.In order to further clarify the influence mechanism of water phase imbibition in shale gas reservoirs,multiple repetitive imbibition experiments were carried out.Based on the changes in rock sample quality caused by mineral dissolution,the visual characteristics of samples from scanning electron microscope,the observation of nuclear magnetic resonance pore structures,and the change of physical properties,the impact of imbibition on the microscopic pore structure,permeability and porosity of shale are revealed.The results show that:(1)Water imbibition causes fractures in shale,thus changing the pore structure;(2)The proportion of macropores increases in shale samples with significantly improved porosity,which indicates that water imbibition will increase the pore space in shale;(3)The imbibition capacity is positively correlated with the porosity and permeability of shale,and the physical properties of shale are significantly improved after imbibition.In addition,the time index is found to be able to quantitatively characterize the influence of imbibition on the pore-throat connectivity of shale.

关 键 词：页岩气藏 裂缝 水相渗吸 物化作用 微观孔隙结构 

分 类 号：TE341[石油与天然气工程—油气田开发工程]