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

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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.