Proper characterization of the mechanical and flow properties of participating rock formations is crucial for subsurface geo-energy projects, including hydrocarbon extraction, geologic carbon storage, and enhanced geothermal systems. Application of mechanical and hydraulic pressures changes the porosity of rock and modifies flow paths. For low-permeable or “tight” rock that mainly contains nanoscale pores and serves as the confining layer for underground storage operations, a significant change in permeability may occur due to a small change in porosity. The pore volume changes in nanoporous geomaterials are extremely difficult to measure directly, but can be assessed from the knowledge of the hydro-mechanical response. Experimental methods to measure the stress-dependent permeability and poroelastic parameters of fluid-saturated tight rock are introduced. Eau Claire shale, Opalinus clay (claystone), and Charcoal granite are selected as representative materials for tight rock and their pore structure and material properties are carefully investigated. The porosity–permeability relationship for tight rock is established by adopting a power-law dependence with the exponent value in the range of 15–17, thus being significantly larger than that for a porous reservoir rock. Consequently, even small perturbations of porosity can cause orders of magnitude changes in permeability possessing a risk on the sealing capacity of the tight formations.

中文翻译：

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致密岩体力学行为与流体流动的耦合

正确表征参与岩层的力学和流动特性对于地下地质能源项目至关重要，包括碳氢化合物开采、地质碳储存和增强地热系统。机械和液压的应用改变了岩石的孔隙度并改变了流动路径。对于以纳米级孔隙为主的低渗透或“致密”岩石，作为地下储库作业的围压层，孔隙率的微小变化可能会导致渗透率发生显着变化。纳米多孔地质材料中的孔隙体积变化极难直接测量，但可以从流体力学响应的知识中进行评估。介绍了测量流体饱和致密岩石的应力相关渗透率和多孔弹性参数的实验方法。选择欧克莱尔页岩、Opalinus 粘土（粘土岩）和木炭花岗岩作为致密岩石的代表性材料，并仔细研究了它们的孔隙结构和材料特性。致密岩石孔隙度-渗透率关系采用幂律关系建立，指数值在15-17范围内，明显大于多孔储层岩石的孔隙度-渗透率关系。因此，即使孔隙度的微小扰动也会导致渗透率发生数量级的变化，从而对致密地层的密封能力造成风险。选择木炭花岗岩作为致密岩石的代表性材料，仔细研究了它们的孔隙结构和材料特性。致密岩石孔隙度-渗透率关系采用幂律关系建立，指数值在15-17范围内，明显大于多孔储层岩石的孔隙度-渗透率关系。因此，即使孔隙度的微小扰动也会导致渗透率发生数量级的变化，从而对致密地层的密封能力造成风险。选择木炭花岗岩作为致密岩石的代表性材料，仔细研究了它们的孔隙结构和材料特性。致密岩石孔隙度-渗透率关系采用幂律关系建立，指数值在15-17范围内，明显大于多孔储层岩石的孔隙度-渗透率关系。因此，即使孔隙度的微小扰动也会导致渗透率发生数量级的变化，从而对致密地层的密封能力造成风险。