页岩层系剪切变形对其孔隙结构的影响研究

Focusing closely on the impact mechanism of shear deformation on the evolution of pore structure in gas shale, shale samples of Upper Ordovician Wufeng Formation - Lower Silurian Longmaxi Formation, which has achieved a breakthrough in marine shale gas in Southern China, were obtained as the main research object. According to the feature of intense deformation of detachment shale zone, the structural deformation characteristics in shale and its control of pore structure evolution as a principal line. We through field investigation, laboratory test method and combining integrated application slipping structural analysis, simulation experiment, rock and mineral microstructure identification, and all scale pore structure analysis techniques in the present study. Furthermore, samples with different structure evolution properties from the Paleozoic strata in Southern China are collected and multi-scale observation and experiment methods are combined to further study the macro to micro scale characteristics, to understand the characteristics and evolution mechanisms of the shale pore structure under shear deformation process. The results can be of great significance in further understanding the scientific connotation of shale reservoir research, and provide a scientific basis of marine shale gas resource assessment problem solving on the detachment structure region in Southern China.

紧密围绕滑脱层剪切变形对页岩储层孔隙结构的影响这一具有理论意义和实践价值的重要科学问题，选择海相页岩气已经获得突破的我国南方上奥陶统五峰组-下志留统龙马溪组页岩地层为主要研究对象。针对页岩滑脱层剪切变形强烈的特点，以滑脱层页岩剪切变形对其储层孔隙结构演化的影响为主线，通过野外考察和室内实验相结合的方法，综合应用构造解析、模拟实验、岩石矿物及显微构造鉴定、孔隙结构全尺度测试等分析技术，厘清滑脱构造背景下页岩剪切变形的宏-微观结构特征；探讨剪切变形作用对页岩储层孔隙结构演化的影响及机理。深化页岩储层演化机理研究的科学内涵，为我国南方构造复杂区海相页岩气资源调查评价难题的解决提供科学依据。

页岩储层的孔隙度、孔隙\裂缝发育与分布、渗透性等孔隙结构相关特征是页岩的重要储层物理性质，这一性质在页岩气赋存运移特征研究和勘探开发评价等方面具有重要理论意义和实践价值。本项目以龙马溪组海相页岩为主要研究对象，采用低温液氮吸附、X射线衍射（XRD）、扫描电镜（SEM）、光学显微镜、甲烷高压等温吸附实验、高温高压多场耦合力学模拟实验等多种分析测试技术，对应力作用背景下剪切变形页岩的宏-微观变形特征、孔隙\裂缝结构、渗透性和甲烷吸附能力等进行了系统分析和详细研究，获得了页岩在应力作用下的剪切变形样式、孔隙结构、渗透性和页岩气效应特征。认识到构造剪切变形是造成相同沉积单元页岩储层物性差异的重要机制，剪切变形作用对页岩储层孔隙演化具有显著影响，首次从页岩结构变形与否的角度，开展变形页岩与原生页岩孔隙结构差异的定量研究，发现构造改造作用造成变形页岩孔隙结构的两极分化，即从原生页岩的均势分布和一定的中孔优势向变形页岩的大孔和微孔两极优势的孔隙结构类型演化；剪切变形作用导致变形页岩中封闭性的无效孔隙的发育和残余气的普遍存在；剪切变形作用和裂缝型孔隙的发育造成页岩储层渗透率的显著提高；挤压应力和剪切变形作用对页岩甲烷吸附能力有弱化作用。这些研究成果拓展了页岩储层发育演化机理研究的研究领域，对揭示我国南方复杂构造区变形页岩储层物性演化机理及复杂构造区页岩气赋存成藏规律具有理论意义和实际应用价值。