Production potential and stability of hydrate-bearing sediments at the site GMGS3-W19 in the South China Sea: A preliminary feasibility study |
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| Institution: | 1. Faculty of Engineering, China University of Geosciences, Wuhan 430074, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;3. Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China;4. Key Laboratory of Gas Hydrate, Ministry of Land and Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;5. College of Engineering, Peking University, Beijing 100871, China;6. Guangzhou Marine Geological Survey, Ministry of Land and Resources, Guangzhou 510760, China;1. Faculty of Engineering, China University of Geosciences, Wuhan 430074, China;2. State Key Laboratory of Enhanced Oil Recovery, Research Institute of Petroleum Exploration and Development, Beijing 100083, China;3. Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China;4. Qingdao Institute of Marine Geology, Ministry of Land and Resources, China;1. Key Laboratory of Fluid-Solid Coupling System Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, China;2. Marine Environmental and Engineering Geological Survey, Guangzhou Marine Geological Survey, Guangzhou, 510075, China;1. MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Ministry of Land and Resources, Guangzhou 510075, China;2. School of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, China;3. China University of Geosciences (Wuhan), Wuhan 430074, China;1. Key Laboratory of Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640, China;2. Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China;3. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, China Academy of Sciences, Wuhan, Hubei, 430071, China;4. Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao, 266071, China;1. Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA;2. Technion – Israel Institute of Technology, Technion City, Haifa 32000, Israel;3. Japan Oil, Gas and Metals National Corporation, 1-2-2 Hamada, Mihama, Chiba 262-0019, Japan |
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| Abstract: | According to the preliminary geological data of gas hydrate bearing-sediments (GHBS) at site GMGS3-W19 in the third Chinese expedition to drill gas hydrates in 2015, a production model using three different recovery pressures was established to assess the production feasibility from both production potential and geomechanical response. The simulation results show that for this special Class 1 deposit, it is a little hard for gas production rate to reach the commercial extraction rate because the degree of hydrate dissociation is limited due to the low reservoir permeability and the permeable burdens. However, the free gas accumulating in the lower part of the GHBS can significantly increase gas-to-water ratio. It also generates many secondary hydrates in the GHBS at the same time. Decreasing the well pressure can be beneficial to gas recovery, but the recovery increase is not obvious. In term of geomechanical response of the reservoir during the gas recovery, the permeable burdens are conducive to reduction of the sediment deformation, though they don't facilitate the gas recovery rate. In addition, significant stress concentration is observed in the upper and lower edges of GHBS around the borehole during depressurization because of high pressure gradient, and the greater the well pressure drop, the more obvious the phenomenon. Yield failures and sand production easily take place in the edges. Therefore, in order to achieve the purpose of safe, efficient and long-term gas production, a balance between the production pressure and reservoir stability should be reached at the hydrate site. The production pressure difference and sand production must be carefully controlled and the high stress concentration zones need strengthening or sand control treatment during gas production. Besides, the sensitivity analyses show that the hydrate saturation heterogeneity can affect the production potential and geomechanical response to some extent, especially the water extraction rate and the effective stress distribution and evolution. Increasing GHBS and its underlying free gas formation permeabilities can enhance the gas production potential, but it probably introduces geomechanical risks to gas recovery operations. |
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| Keywords: | Gas hydrate Production potential Geomechanical response Numerical simulation |
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