Effects of Stress on the Anisotropic Development of Permeability During Mechanical Compaction of Porous Limestones

本文描述了多孔碳酸盐岩在机械压实过程中应力诱导渗透率各向异性的实验研究，这将为地壳变形和流体流动之间的耦合提供新的见解。用于表征应力诱导渗透率各向异性的方法是在相同压力和温度条件下进行常规拉伸和混合压缩试验。由于两种试验的加载路径重合，因此比较两种试验的渗透率值可以定量估计渗透率各向异性随有效平均应力和差应力的变化情况。具体任务包括：1)对印第安纳和索恩霍芬石灰石进行常规三轴拉伸试验；2)分别对印第安纳和索恩霍芬灰岩进行混合三轴压缩试验；3)对变形试样进行显微组织观察。本研究的重点是研究高温下多孔灰岩破坏后的非弹性行为和渗透率各向异性的演化。目标是建立渗透率演化与破坏微观机制之间的动态联系，这对于理解许多孕震、沉积和变质过程至关重要。拟议活动的更广泛影响拟议的研究将产生关于应力如何影响地壳岩石的输运特性（孔隙度和渗透率）的实验数据。这些数据将引起许多学科的科学家的兴趣。除此之外，拟议的研究将为了解断层力学、提高资源采收率和预测储层稳定性提供有用的数据。通过网站、演讲、讨论和实践实验，PI将让研究生、本科生（通过WHOI暑期学生奖学金计划）、少数民族学生和当地高中生参与拟议的研究。通过这些教育和推广活动，拟议的研究将成为培养和培训未来研究人员的平台。

Intellectual MeritThis proposal describes an experimental study of stress-induced permeability anisotropy during mechanical compaction in porous carbonate rocks that will provide new insights into the coupling between deformation and fluid flow in the Earth's crust. The methodology used to characterize stress-induced permeability anisotropy is to conduct both conventional extension and hybrid compression tests at the same pressure and temperature conditions. Since their loading paths coincide, the comparison of permeability values from the two types of tests provides quantitative estimates of the development of permeability anisotropy as function of effective mean and differential stresses. Specific tasks include: 1) to conduct conventional triaxial extension tests on both Indiana and Solnhofen limestones; 2) to conduct hybrid triaxial compression tests on both Indiana and Solnhofen limestones; 3) to conduct microstructural observation on the deformed samples. The focus of this study is to investigate the inelastic behavior and the evolution of permeability anisotropy upon failure in porous limestones at elevated temperature. The goal is to establish dynamic links between the evolution of permeability and the micromechanisms of failure, which is essential in understanding many seismogenic, sedimentary and metamorphic processes. Broader Impacts of the Proposed ActivityThe proposed study will generate experimental data on how stress affects transport properties (porosity and permeability) in crustal rocks. The data will be of interest to scientists in many disciplines. Among other things, the proposed study will provide data that are useful for understanding fault mechanics, improving resource recovery, and predicting reservoir stability. Through websites, presentations, discussions and hands-on experiments, the PI will involve graduate students, undergraduate students (through WHOI summer student fellowship program), minority students and local high school students in the proposed study. Through these education and outreach activities, the proposed research will serve as a platform for cultivating and training researchers of the future.