Fracture development in Paleozoic shale of Chongqing area (South China). Part two: Numerical simulation of tectonic stress field and prediction of fractures distribution |
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| Institution: | 1. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;2. Structural Research Center of Oil & Gas Bearing Basin, Ministry of Education, Hangzhou 310027, China;3. Department of Geology & Environmental Earth Science, Miami University, Oxford, OH 45056, USA;4. Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;1. School of Energy Resources, China University of Geosciences, Beijing 100083, China;2. Key Laboratory for Marine Reservoir Evolution and Hydrocarbon Abundance Mechanism, Ministry of Education, China University of Geosciences, Beijing 100083, China;3. Beijing Key Laboratory of Unconventional Natural Gas Geology Evaluation and Development Engineering, China University of Geosciences, Beijing 100083, China;4. Key Laboratory for Shale Gas Exploitation and Assessment, Ministry of Land and Resources, China University of Geosciences, Beijing 100083, China;5. School of Geosciences, China University of Petroleum, Qingdao 266580, China;6. Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, China;7. Eighth Oil Production Factory, Daqing Oilfield Company, Ltd., PetroChina, Daqing 163514, China |
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| Abstract: | A tectonics sedimentation evolution has been researched in Southeast Chongqing, and the reasonable Longmaxi shale highstand system tract (HST) and transgressive system tract (TST) geological model were built respectively based on the rock mechanical test and acoustic emission experiment which the samples are from field outcrop and the Yuye-1 well. The Longmaxi shale two-dimension tectonic stress field during the Cenozoic was simulated by the finite element method, and the distribution of fractures was predicted. The research results show that the tectonic stress field and the distribution of fractures were controlled by lithology and structure. As a result of Cretaceous movement, there are trough-like folds (wide spaced synclines), battlement-like folds (similar spaces between synclines and anticlines) and ejective folds (wide spaced anticlines), which are regularly distributed from southeast to northwest in the study area. Since the strain rate and other physical factors such as the viscosity are not taken into account, and the stress intensity is the main factor that determines the tectonic strength. Therefore, the stronger tectonic strength leads the higher stress intensity in the eastern and southeastern study area than in the northwest. The fracture zones are mainly concentrated in the fold axis, transition locations of faults and folds, the regions where are adjacent to faults. The fragile mineral contents (such as siliceous rock, carbonate rock and feldspar) in the shelf facies shale from south of the study area are higher than in the bathyal facies and abyssal facies shale from center of the study area. The shales characterized by low Poisson’s ratio and high elastic modulus from south of the study area are easily broken during Cenozoic orogenic movement. |
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| Keywords: | Longmaxi Shale Mechanical rock properties Tectonic stress field Fractures distribution Southeast Chongqing |
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