考虑断裂韧性影响的页岩气储层可压性评价方法  

Evaluation method of compressibility of shale gas reservoir in consideration of the influence of fracture toughness

作　　者：张辰庆 许江[1,2] 彭守建[1,2] 闫发志 吴斌[1,2] 岳雨晴 ZHANG Chenqing;XU Jiang;PENG Shoujian;YAN Fazhi;WU Bin;YUE Yuqing(State Key Laboratory of Coal Mine Disaster Dynamics and Control of Chongqing University,Chongqing 400044,China;State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam of Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044 [2]重庆大学复杂煤层气瓦斯抽采国家地方联合工程实验室,重庆400044

出　　处：《煤田地质与勘探》2019年第5期131-137,共7页Coal Geology & Exploration

基　　金：国家自然科学基金面上项目(51874055);重庆市重点产业共性关键技术创新专项(cstc2016zdcy-zd90002)~~

摘　　要：可压性是衡量页岩气储层对压裂改造响应程度的重要依据,目前针对页岩可压性常用脆性指数对其进行评价。但在实际运用中存在脆性指数相近,实际压裂效果却差别甚远的问题。为了弥补利用脆性指数进行页岩气储层可压性评价的不足,在考虑断裂韧性影响的基础上引入临界机械能释放率,综合了Ⅰ型、Ⅱ型断裂韧性对岩石裂缝发育的影响,并定义平均临界机械能释放率。最后结合平均临界机械能释放率和脆性指数,初步建立了以裂缝发育指数为量化指标的页岩气储层可压性评价模型。基于焦石坝龙马溪组焦页48-2HF井测井资料,计算出其弹性模量、泊松比、Ⅰ型及Ⅱ型断裂韧性,并根据构建的裂缝发育指数模型,得出页岩储层可压性随埋深的变化关系。结合现场微震资料,验证了该模型能有效预测页岩气储层可压性随埋深的变化趋势,为页岩气实际开发过程中优选页岩储层压裂段提供可靠方法。Compressibility is an important basis for measuring the response of shale gas reservoirs to hydraulic fracturing.Currently,the brittleness index commonly used for shale compressibility has been evaluated.However,in practice,there are problems in which the brittleness index is similar and the actual fracturing effect is far different.In order to make up for the lack of brittleness index for the evaluation of compressibility of shale gas reservoirs,this study incorporated critical mechanical energy release rate in consideration of the influence of fracture toughness,and defined the average critical mechanical energy release rate of the integrated modes I and II of fracture toughness of rock fracture development.Finally,combined with the average critical mechanical energy release rate and brittleness index,the compressibility evaluation model of shale gas reservoir with fracture development index as the quantitative index was established.The elasticity modulus,Poisson’s ratio,modes I and II of fracture toughness were calculated based on the logging data of well 48-2HF in Longmaxi Formation in Jiaoshiba.According to the constructed fracture development index model,the variation of the compressibility of shale reservoirs with the burial depth was obtained.Combined with on-site microseismic data,it is verified that the model could effectively predict the change trend of the compressibility of shale gas reservoir with burial depth,and provide a reliable method for optimization of shale reservoir fracturing interval in the actual development of shale gas.

关 键 词：页岩气储层 可压性评价 脆性指数 断裂韧性 裂缝发育指数 龙马溪组 四川焦石坝 

分 类 号：TE321[石油与天然气工程—油气田开发工程]