Qualitative and quantitative characterization of a transitional shale reservoir: A case study from the Upper Carboniferous Taiyuan shale in the eastern uplift of Liaohe Depression,China |
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| Institution: | 1. School of Energy Resources, China University of Geosciences (Beijing), Beijing, 100083, China;2. PetroChina Research Institute of Petroleum Exploration and Development, Langfang, Hebei, 065007, China;3. National Energy Shale Gas R&D (Experiment) Centre, Hebei, 065007, China;4. PetroChina Research Institute of Petroleum Exploration and Development, Beijing, 100083, China;5. Energy & Geoscience Institute, University of Utah, Salt Lake City, UT, 84108, USA;1. Department of Geology, College of Sciences, China University of Petroleum, Beijing 102249, China;2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China;3. College of Earth Sciences, Northeast Petroleum University, Daqing, Heilongjiang 163318, China;1. College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061, China;2. Geo-Energy Research Institute, Qingdao University of Science and Technology, Qingdao 266109, China;3. College of Automation and Electronic Engineering, Qingdao University of Science and Technology, Qingdao 266042, China;1. Basin and Reservoir Research Center, China University of Petroleum, Beijing 102249, China;2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;3. Research Institute of Petroleum Exploration & Production, SINOPEC, Beijing 100083, China;4. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The paper takes the Upper Carboniferous Taiyuan shale in eastern uplift of Liaohe depression as an example to qualitatively and quantitatively characterize the transitional (coal-associated coastal swamp) shale reservoir. Focused Ion Beam Scanning Electron Microscope (FIB-SEM), nano-CT, helium pycnometry, high-pressure mercury intrusion and low-pressure gas (N2 & CO2) adsorption for eight shale samples were taken to investigate the pore structures. Four types of pores, i.e., organic matter (OM) pores, interparticle (InterP) pores, intraparticle (IntraP) pores and micro-fractures are identified in the shale reservoir. Among them, intraP pores and micro-fractures are the major pore types. Slit-shaped pores are the major shape in the pore system, and the connectivity of the pore-throat system is interpreted to be moderate, which is subordinate to marine shale. The porosity from three dimension (3D) reconstruction of SEM images is lower than the porosity of helium pycnometry, while the porosity trend of the above two methods is the same. Combination of mercury intrusion and gas absorption reveals that nanometer-scale pores provide the main storage space, accounting for 87.16% of the pore volume and 99.85% of the surface area. Micropores contribute 34.74% of the total pore volume and 74.92% of the total pore surface area; and mesopores account for 48.27% of the total pore volume and 24.93% of the total pore surface area; and macropores contribute 16.99% of the total pore volume and 0.15% of the total pore surface area. Pores with a diameter of less than 10 nm contribute the most to the pore volume and the surface area, accounting for 70.29% and 97.70%, respectively. Based on single factor analysis, clay minerals are positively related to the volume and surface area of micropores, mesopores and macropores, which finally control the free gas in pores and adsorbed gas content on surface area. Unlike marine shale, TOC contributes little to the development of micropores. Brittle minerals inhibit pore development of Taiyuan shale, which proves the influence of clay minerals in the pore system. |
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| Keywords: | Taiyuan shale Pore types classification Pore structure Controlling factors |
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