Natural gas hydrates (NGHs) are a new type of clean energy with great development potential. However, it is urgent to achieve safe and economical NGHs development and utilization. This study established a physical model of the study area using the FLAC3D software based on the key parameters of the NGHs production test area in the South China Sea, including the depressurization method, and mechanical parameters of strata, NGHs occurrence characteristics, and the technological characteristics of horizontal wells. Moreover, this study explored the law of influences of the NGHs dissociation range on the stability of the overburden strata and the casing structure of a horizontal well. The results are as follows. With the dissociation of NGHs, the overburden strata of the NGHs dissociation zone subsided and formed funnel-shaped zones and then gradually stabilized. However, the upper interface of the NGHs dissociation zone showed significant redistribution and discontinuity of stress. Specifically, distinct stress concentration and corresponding large deformation occurred in the build-up section of the horizontal well, which was thus prone to suffering shear failure. Moreover, apparent end effects occurred at the end of the horizontal well section and might cause the deformation and failure of the casing structure. Therefore, it is necessary to take measures in the build-up section and at the end of the horizontal section of the horizontal well to prevent damage and ensure the wellbore safety in the long-term NGHs exploitation.

Peng-fei Xie;Lin Yang;Qian-yong Liang;Xu-hui Zhang;Liang-hua Zhang;Bin Zhang;Xiao-bing Lu;Hui-ce He;Xue-min Wu;Yi-fei Dong

Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;Institute of Mechanics,Chinese Academy of Sciences,Beijing 100190,China;China University of Geosciences(Beijing),Beijing 100084,China;Guangzhou Marine Geological Survey,China Geological Survey,Ministry of Natural Resources,Guangzhou 510760,China;National Engineering Research Center of Gas Hydrate Exploration and Development,Guangzhou 511400,China;University of Chinese Academy of Sciences,Beijing 100049,China

中国地质（英文）

[1]Peng-fei Xie;Lin Yang;Qian-yong Liang;Xu-hui Zhang;Liang-hua Zhang;Bin Zhang;Xiao-bing Lu;Hui-ce He;Xue-min Wu;Yi-fei Dong-.Stability analysis of seabed strata and casing structure during the natural gas hydrates exploitation by depressurization in horizontal wells in South China Sea)[J].中国地质（英文）,2022(02):300-309

NGHs

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