Characterization of electrical properties of organic-rich shales at nano/micro scales |
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| Institution: | 1. Harold Vance Department of Petroleum Engineering, Texas A&M University, College Station, TX 77843, USA;2. Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA;3. Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA;1. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China;2. School of Resources and Geoscience, China University of Mining and Technology, Xuzhou, 221116, China;1. Division of Plastic Surgery, Department of Surgery, Northwell Health, 1991 Marcus Avenue, Suite 102, North New Hyde Park, NY 11042-2062, USA;2. Private Practice, 9000 Waukegan Road, Suite 210, Morton Grove, IL 60053, USA;1. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan 430074, China;2. Department of Earth and Environmental Sciences, The University of Texas at Arlington, Arlington, TX 76019, USA;3. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China;4. Exploration Company, Sinopec, Chengdu 610064, China;5. Petroleum Exploration and Development, Jianghan Oilfield Branch Company, Sinopec, Wuhan 430223, China;1. Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, University Station, Box X, Austin, TX 78713, USA;2. Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, 1 University Station, Austin, TX 78712, USA;1. Research Institute of Petroleum Exploration and Development of SINOPEC, Beijing, China;2. The Unconventional Oil and Gas Institute, China University of Petroleum (Beijing), Beijing, China |
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| Abstract: | A new experimental protocol is explored to characterize electrical properties of hydrocarbon-bearing mudrocks at nano/micro scales. Two current flow regimes of peak force - tunneling atomic force microscopy (PF-TUNA) have been used: (1) the vertical out-of-plane current regime with hundred micrometer diameter top electrodes obtains homogenized conductivity quantitatively, (2) the horizontal in-plane current regime was shown powerful to visualize the conductive paths (related to connectivity and tortuosity) for heterogeneous and anisotropic shales. Results show that the approach works well with one to two layers of adsorbed water (25–55% relative humidity) under low frequency (0.5–20 Hz) for shale rocks. Current maps with sub-nanometer resolution emphasize the dominant role of hydrated ions associated with the hydrophilic clay minerals in driving the dielectric response of shales, while conductivity of pyrite and kerogen cannot be neglected for mature organic-rich shale conductive network. The acquired I-V curves at microscale provide a reliable mean to evaluate homogenized conductivity of such multiscale multi-component heterogeneous material under controlled environmental conditions. The procedure discussed herein serves as a complement for fine grained rocks and minerals of ionic-electronic hybrid conductive mechanism under partially water saturation. These results can be used to develop accurate electrical models, specifically for shale rocks with heterogeneous and sophisticated microstructure. The methodology can be also extended to other micro- or meso-porous geomaterials such as cementitious and bituminous nanoporous media. |
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| Keywords: | PF-TUNA Humidity Polarization Resistivity Shale rocks Anisotropy Tortuosity |
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