Mechanism of gas hydrate accumulation and its potential geological hazard risk in the northern accretionary wedge of Manila Trench

Ju Dong; Gao Hongfang; Li Xuejie

doi:10.12284/hyxb2024004

Article Contents

Article Navigation > Haiyang Xuebao > 2024 >

Ju Dong，Gao Hongfang，Li Xuejie. Mechanism of gas hydrate accumulation and its potential geological hazard risk in the northern accretionary wedge of Manila Trench[J]. Haiyang Xuebao，2024, 46(3)：1–11 doi: 10.12284/hyxb2024004

Citation:

PDF( 4546 KB)

Mechanism of gas hydrate accumulation and its potential geological hazard risk in the northern accretionary wedge of Manila Trench

doi: 10.12284/hyxb2024004

Ju Dong^{1, 2
,},
Gao Hongfang^{1, 2
,
,},
Li Xuejie^{1, 2}

1.
Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
2.
Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China

Received Date: 2023-05-19
Rev Recd Date: 2023-08-31

Available Online: 2024-04-15

Abstract

Abstract

Natural gas hydrates have received widespread attention due to their enormous resource potential, but previous researches have focused mostly on the passive continental margin in the northern South China Sea, while rarely on the active continental margin in the eastern South China Sea. Based on the analysis of multi-channel seismic profiles in the active continental margin area of the Manila Trench in northeast of the South China Sea, this paper identified typical gas hydrate indicators such as bottom simulating reflector, blanking zone, polarity-reversal, and fluid migration channels, such as reverse fault and mud diapir are identified in this paper. The Orogenic Belt in southwestern Taiwan is an extension of the accretionary wedge of the Manila Trench. The associated gas of mud volcano is mainly CH₄ and minorly showing high nitrogen anomaly. The geochemical characteristics of the associated gas show that natural gas in this area is mainly mature hydrocarbon gas of pyrolysis origin, and is mainly the contribution of Neogene thick marine sedimentary source rock. According to the analysis, the cause is that the plate subduction brought deep hydrocarbon into the accretionary wedge and formed a high-pressure environment. The thermally generated hydrocarbon gas migrated upward along mud diapir and reverse fault. During the migration, some natural gas was gradually transformed by decomposition of microorganisms and mixed with in-situ microbial gas. The thermogenic and biogenic methane eventually mixed in the suitable stable zone to form a mixed gas hydrate reservoir dominated by thermogenic and partly biogenic. In addition, with the change of external environment and the continuous activities of subduction movement, the stability of natural gas hydrate is damaged and decomposition leakage occurs, which may cause landslide. In the further exploration and development of natural gas hydrate resources in this area, we must pay attention to the potential geological disaster risk.
- gas hydrate,
- accumulation mechanism,
- accretive wedge of Manila Trench,
- active continental margin,
- South China Sea

FullText(HTML)

References(61)

References

[1]	王淑玲, 孙张涛. 全球天然气水合物勘查试采研究现状及发展趋势[J]. 海洋地质前沿, 2018, 34(7): 24−32. Wang Shuling, Sun Zhangtao. Current status and future trends of exploration and pilot production of gas hydrate in the world[J]. Marine Geology Frontiers, 2018, 34(7): 24−32.
[2]	聂云峰, 于晶, 陈宏文, 等. 北极斯瓦尔巴特群岛及邻区天然气水合物分解对气候、海洋环境和生物的影响[J]. 现代地质, 2018, 32(5): 1012−1024. Nie Yunfeng, Yu Jing, Chen Hongwen, et al. Climatic, environmental and biological impacts of gas hydrate decomposition in Arctic Svalbard and its surrounding areas[J]. Geoscience, 2018, 32(5): 1012−1024.
[3]	潘一, 杨双春. 天然气水合物研究进展[J]. 当代化工, 2012, 41(4): 401−404. Pan Yi, Yang Shuangchun. Research progress in natural gas hydrates[J]. Contemporary Chemical Industry, 2012, 41(4): 401−404.
[4]	赵伟, 王全胜, 郑星升. 国内天然气水合物研究进展[J]. 石化技术, 2019, 26(10): 165−167. Zhao Wei, Wang Quansheng, Zheng Xingsheng. Research progress on natural gas hydrate in China[J]. Petrochemical Industry Technology, 2019, 26(10): 165−167.
[5]	Liu Changling, Meng Qingguo, He Xingliang, et al. Characterization of natural gas hydrate recovered from Pearl River Mouth Basin in South China Sea[J]. Marine and Petroleum Geology, 2015, 61: 14−21. doi: 10.1016/j.marpetgeo.2014.11.006
[6]	Yu Xinghe, Wang Jianzhong, Liang Jinqiang, et al. Depositional characteristics and accumulation model of gas hydrates in northern South China Sea[J]. Marine and Petroleum Geology, 2014, 56: 74−86. doi: 10.1016/j.marpetgeo.2014.03.011
[7]	杨胜雄, 梁金强, 陆敬安, 等. 南海北部神狐海域天然气水合物成藏特征及主控因素新认识[J]. 地学前缘, 2017, 24(4): 1−14. Yang Shengxiong, Liang Jinqiang, Lu Jingan, et al. New understandings on the characteristics and controlling factors of gas hydrate reservoirs in the Shenhu Area on the northern slope of the South China Sea[J]. Earth Science Frontiers, 2017, 24(4): 1−14.
[8]	匡增桂, 郭依群. 南海北部神狐海域新近系以来沉积相及水合物成藏模式[J]. 地球科学− 中国地质大学学报, 2011, 36(5): 914−920. Kuang Zenggui, Guo Yiqun. The sedimentary facies and gas hydrate accumulation models since Neogene of Shenhu Sea Area, northern South China Sea[J]. Earth Science: Journal of China University of Geosciences, 2011, 36(5): 914−920.
[9]	张光学, 陈芳, 沙志彬, 等. 南海东北部天然气水合物成藏演化地质过程[J]. 地学前缘, 2017, 24(4): 15−23. Zhang Guangxue, Chen Fang, Sha Zhibin, et al. The geological evolution process of natural gas hydrate reservoirs in the northeastern South China Sea[J]. Earth Science Frontiers, 2017, 24(4): 15−23.
[10]	张伟, 梁金强, 陆敬安, 等. 中国南海北部神狐海域高饱和度天然气水合物成藏特征及机制[J]. 石油勘探与开发, 2017, 44(5): 670−680. Zhang Wei, Liang Jinqiang, Lu Jingan, et al. Accumulation features and mechanisms of high saturation natural gas hydrate in Shenhu Area, northern South China Sea[J]. Petroleum Exploration and Development, 2017, 44(5): 670−680.
[11]	沙志彬, 梁金强, 苏丕波, 等. 珠江口盆地东部海域天然气水合物钻探结果及其成藏要素研究[J]. 地学前缘, 2015, 22(6): 125−135. Sha Zhibin, Liang Jinqiang, Su Pibo, et al. Natural gas hydrate accumulation elements and drilling results analysis in the eastern part of the Pearl River Mouth Basin[J]. Earth Science Frontiers, 2015, 22(6): 125−135.
[12]	邓辉. 台湾西南海域地震数据处理及天然气水合物识别[D]. 广州: 中国科学院广州地球化学研究所, 2006. Deng Hui. Seismic data processing and identifying for gas hydrate offshore Southwest Taiwan[D]. Guangzhou: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 2006.
[13]	丁巍伟, 陈汉林, 王渝民, 等. 台湾增生楔天然气水合物的地震特征[J]. 海洋与湖沼, 2006, 37(1): 90−96. Ding Weiwei, Chen Hanlin, Wang Yumin, et al. Geophysical features of gas hydrate in Taiwan Accretionary prism, South China Sea[J]. Oceanologia et Limnologia Sinica, 2006, 37(1): 90−96.
[14]	尚继宏, 李家彪. 南海东北部陆坡与恒春海脊天然气水合物分布的地震反射特征对比[J]. 海洋学研究, 2006, 24(4): 12−20. doi: 10.3969/j.issn.1001-909X.2006.04.002 Shang Jihong, Li Jiabiao. A study on the seismic reflection of the gas hydrate distribution at the northeast SCS slope and Hengchun Ridge[J]. Journal of Marine Sciences, 2006, 24(4): 12−20. doi: 10.3969/j.issn.1001-909X.2006.04.002
[15]	李家彪, 金翔龙, 阮爱国, 等. 马尼拉海沟增生楔中段的挤入构造[J]. 科学通报, 2004, 49(10): 1000− 1008. Li Jiabiao, Jin Xianglong, Ruan Aiguo, et al. Indentation tectonics in the accretionary wedge of middle Manila Trench[J]. Chinese Science Bulletin, 2004, 49(110): 1000−1008.
[16]	高金尉, 吴时国, 姚永坚, 等. 马尼拉俯冲带北段增生楔前缘构造变形和精细结构[J]. 地球物理学报, 2018, 61(7): 2845−2858. Gao Jinwei, Wu Shiguo, Yao Yongjian, et al. Tectonic deformation and fine structure of the frontal accretionary wedge, northern Manila subduction zone[J]. Chinese Journal of Geophysics, 2018, 61(7): 2845−2858.
[17]	王红丽, 赵强, 黄金莲, 等. 马尼拉俯冲带北段增生楔形态结构及演化过程[J]. 海洋科学, 2019, 43(8): 1−16. Wang Hongli, Zhao Qiang, Huang Jinlian, et al. Morphological structure and evolution of accretionary wedge in the northern part of Manila subduction zone[J]. Marine Sciences, 2019, 43(8): 1−16.
[18]	王哲, 李学杰, 高红芳, 等. 马尼拉俯冲带北段前渊构造层特征及构造含义[J]. 桂林理工大学学报, 2020, 40(2): 278−283. Wang Zhe, Li Xuejie, Gao Hongfang, et al. Characteristics and tectonic implications of structural layers in foredeep of the northern segment of Manila subduction zone[J]. Journal of Guilin University of Technology, 2020, 40(2): 278−283.
[19]	Sella G F, Dixon T H, Mao Ailin. REVEL: a model for recent plate velocities from space geodesy[J]. Journal of Geophysical Research: Solid Earth, 2002, 107(B4): 2081.
[20]	Lallemand S, Liu C S. Geodynamic implications of present-day kinematics in the southern Ryukyus[J]. Journal of the Geological Society of China, 1998, 41(4): 551−564.
[21]	Yu S B, Chen H Y, Kuo Longchen. Velocity field of GPS stations in the Taiwan Area[J]. Tectonophysics, 1997, 274(1/3): 41−59.
[22]	Seno T, Stein S, Gripp A E. A model for the motion of the Philippine Sea Plate consistent with NUVEL-1 and geological data[J]. Journal of Geophysical Research: Solid Earth, 1993, 98(B10): 17941−17948. doi: 10.1029/93JB00782
[23]	Seno T. The instantaneous rotation vector of the Philippine Sea Plate relative to the Eurasian Plate[J]. Tectonophysics, 1977, 42(2/4): 209−226.
[24]	Suppe J. The active Taiwan Mountain Belt[M]//Schaer J P, Rodgers J. The Anatomy of Mountain Ranges. Princeton: Princeton University Press, 1987.
[25]	Hayes D E, Lewis S D. A geophysical study of the Manila Trench, Luzon, Philippines: 1. Crustal structure, gravity, and regional tectonic evolution[J]. Journal of Geophysical Research: Solid Earth, 1984, 89(B11): 9171−9195. doi: 10.1029/JB089iB11p09171
[26]	丁巍伟, 陈汉林, 杨树锋, 等. 南海西南次海盆与东部次海盆地质与地球物理分析[J]. 高校地质学报, 2002, 8(3): 268−279. Ding Weiwei, Chen Hanlin, Yang Shufeng, et al. Geological and geophysical analysis of the southwestern and eastern sub-basins, South China Sea[J]. Geological Journal of China Universities, 2002, 8(3): 268−279.
[27]	Hall R, Wilson M E J. Neogene sutures in eastern Indonesia[J]. Journal of Asian Earth Sciences, 2000, 18(6): 781−808. doi: 10.1016/S1367-9120(00)00040-7
[28]	Lin Chechuan, Lin A T S, Liu C , et al. Geological controls on BSR occurrences in the incipient arc-continent collision zone off Southwest Taiwan[J]. Marine and Petroleum Geology, 2009, 26(7): 1118−1131.
[29]	罗敏, 王宏斌, 杨胜雄, 等. 南海天然气水合物研究进展[J]. 矿物岩石地球化学通报, 2013, 32(1): 56−69. Luo Min, Wang Hongbin, Yang Shengxiong, et al. Research advancement of natural gas hydrate in South China Sea[J]. Bulletin of Mineralogy, Petrology and Geochemistry, 2013, 32(1): 56−69.
[30]	董马超. 海底天然气水合物及与其有关的地震反射[J]. 石油化工应用, 2015, 34(12): 70−73. Dong Machao. Marine natural gas hydrate and concerned seismic reflection[J]. Petrochemical Industry Application, 2015, 34(12): 70−73.
[31]	焦春波. 珠江口盆地东部天然气水合物地震识别依据[J]. 辽宁化工, 2016, 45(11): 1391−1393. Jiao Chunbo. Identification of gas hydrate based on geological and seismic methods in the eastern Pearl River Mouth Basin[J]. Liaoning Chemical Industry, 2016, 45(11): 1391−1393.
[32]	李丽, 杨志力, 吴敬武, 等. 西沙海域似海底反射地震特征及分布控制因素[C]//2019油气田勘探与开发国际会议论文集. 西安:[s.n.], 2019: 493−494. Li Li, Yang Zhili, Wu Jingwu, et al. Characteristics and distribution control factors of submarine reflection seismic in Xisha Sea Are[C]//Proceedings of the 2019 International Conference on Oil and Gas Exploration and Development. Xi’an: [s.n.], 2019: 493−494.
[33]	王霄飞. 南海北部陆坡东西段新构造的异同及对BSR分布的影响[D]. 青岛: 中国海洋大学, 2014. Wang Xiaofei. Similarities and differences of neotectonics of the northern South China Sea slope and its effection of the distribution of BSR[D]. Qingdao: Ocean University of China, 2014.
[34]	辛福兵. 南海西北部陆坡区BSR特征[J]. 辽宁化工, 2018, 47(10): 1071−1073. doi: 10.3969/j.issn.1004-0935.2018.10.030 Xin Fubing. BSR characteristics of the slope area in the northwestern of the South China Sea[J]. Liaoning Chemical Industry, 2018, 47(10): 1071−1073. doi: 10.3969/j.issn.1004-0935.2018.10.030
[35]	张建国, 刘怀山, 岳家彤. 不同震源对天然气水合物的响应特征分析[C]//第十三届国家安全(军事)地球物理学术研讨会论文集. 西安: 2017: 273−277. Zhang Jianguo, Liu Huaishan, Yue Jiatong. Analysis of response characteristics of different seismic sources to natural gas hydrate[C]//Proceedings of the 13th National Security (Military) Geophysical Symposium. Xi’an: Xi'an Map Publishing House, 2017: 273−277.
[36]	Zhang Ruwei, Li Hongqi, Zhang Baojin, et al. Detection of gas hydrate sediments using prestack seismic AVA inversion[J]. Applied Geophysics, 2015, 12(3): 453−464, 470. doi: 10.1007/s11770-015-0503-3
[37]	张旭东. 琼东南海域天然气水合物地震反射特征[J]. 物探与化探, 2014, 38(6): 1152−1158. Zhang Xudong. The seismic reflection characteristics of gas hydrate in Southeast Hainan Sea Area of the South China Sea[J]. Geophysical and Geochemical Exploration, 2014, 38(6): 1152−1158.
[38]	许威, 邱楠生, 孙长宇, 等. 南海天然气水合物稳定带厚度分布特征[J]. 现代地质, 2010, 24(3): 467−473. doi: 10.3969/j.issn.1000-8527.2010.03.008 Xu Wei, Qiu Nansheng, Sun Changyu, et al. The distribution characteristics of the thickness of gas hydrate stability zone in South China Sea[J]. Geoscience, 2010, 24(3): 467−473. doi: 10.3969/j.issn.1000-8527.2010.03.008
[39]	陈志豪, 吴能友, 李家彪. 马尼拉海沟俯冲带增生楔中天然气水合物的流体运移通道[J]. 现代地质, 2010, 24(3): 441−449. Chen Zhihao, Wu Nengyou, Li Jiabiao. Pathway of fluid migration for gas hydrate in the accretionary wedge of manila subduction zone, northeastern South China Sea[J]. Geoscience, 2010, 24(3): 441−449.
[40]	张光学, 黄永样, 祝有海, 等. 活动大陆边缘水合物分布规律及成藏过程[J]. 海洋地质动态, 2001, 17(7): 3−7. Zhang Guangxue, Huang Yongyang, Zhu Youhai, et al. Distribution pattern and reservoir formation process of active continental margin hydrates[J]. Marine Geology Frontiers, 2001, 17(7): 3−7.
[41]	Huang Chiyue, Wu Weiyu, Chang C P, et al. Tectonic evolution of accretionary prism in the arc-continent collision terrane of Taiwan[J]. Tectonophysics, 1997, 281(1/2): 31−51.
[42]	Yang T F, Yeh G H, Fu C C, et al. Composition and exhalation flux of gases from mud volcanoes in Taiwan[J]. Environmental Geology, 2004, 46(8): 1003−1011. doi: 10.1007/s00254-004-1086-0
[43]	戴金星, 吴小奇, 倪云燕, 等. 准噶尔盆地南缘泥火山天然气的地球化学特征[J]. 中国科学: 地球科学, 2012, 42(2): 178−190. Dai Jinxing, Wu Xiaoqi, Ni Yunyan, et al. Geochemical characteristics of natural gas from mud volcanoes in the southern Junggar Basin[J]. Science China: Earth Sciences, 2012, 55(3): 355−367.
[44]	何家雄, 崔洁, 翁荣南, 等. 台湾南部泥火山与伴生气地质地球化学特征及其油气地质意义[J]. 天然气地球科学, 2012, 23(2): 319−326. He Jiaxiong, Cui Jie, Weng Rongnan, et al. Geology of mud volcanoes and geochemistry of associated gas in southern Taiwan and its significance to petroleum geology[J]. Natural Gas Geoscience, 2012, 23(2): 319−326.
[45]	Chao H C, You Chenfeng, Sun C H. Gases in Taiwan mud volcanoes: chemical composition, methane carbon isotopes, and gas fluxes[J]. Applied Geochemistry, 2010, 25(3): 428−436. doi: 10.1016/j.apgeochem.2009.12.009
[46]	孙涛, 李清平, 丁蓉, 等. 南海北部神狐海域天然气水合物气源混合类型及定量表征[J]. 新能源进展, 2021, 9(3): 226−231. Sun Tao, Li Qingping, Ding Rong, et al. Gas source mixing types and quantitative characterization of natural gas hydrate in Shenhu Area, northern of South China Sea[J]. Advances in New and Renewable Energy, 2021, 9(3): 226−231.
[47]	张小军, 陶明信, 王万春, 等. 生物成因煤层气的生成及其资源意义[J]. 矿物岩石地球化学通报, 2004, 23(2): 166−171. Zhang Xiaojun, Tao Mingxin, Wang Wanchun, et al. Generation of biogenic coalbed gases and its significance to resources[J]. Bulletin of Mineralogy, Petrology and Geochemistry, 2004, 23(2): 166−171.
[48]	戴金星, 裴锡古, 戚厚发. 中国天然气地质学: 卷一[M]. 北京: 石油工业出版社, 1992. Dai Jinxing, Pei Xigu, Qi Houfa. Natural Gas Geology in China: Volume 1[M]. Beijing: Petroleum Industry Press, 1992.
[49]	杨玉峰, 雷怀彦. 南海北部台西南盆地973-4岩芯碳的地球化学特征[J]. 海洋科学, 2016, 40(8): 100−107. Yang Yufeng, Lei Huaiyan. Geochemical characteristics of carbon in core 973-4 from southwestern Taiwan Basin in northern South China Sea[J]. Marine Sciences, 2016, 40(8): 100−107.
[50]	蒋雨函, 高小其, 王阳洋, 等. 中国新疆北天山和台湾南部陆地泥火山研究进展[J]. 地震, 2020, 40(3): 65−82. Jiang Yuhan, Gao Xiaoqi, Wang Yangyang, et al. A review of researches on land mud volcanoes in northern Tianshan of Xinjiang and southern Taiwan, China[J]. Earthquake, 2020, 40(3): 65−82.
[51]	何家雄, 夏斌, 陈恭洋, 等. 台西南盆地中新生界石油地质与油气勘探前景[J]. 新疆石油地质, 2006, 27(4): 398−402. He Jiaxiong, Xia Bin, Chen Gongyang, et al. Petroleum geology and exploration prospect of Mesozoic and Cenozoic in Taixinan Basin, northern South China Sea[J]. Xinjiang Petroleum Geology, 2006, 27(4): 398−402.
[52]	何家雄, 夏斌, 王志欣, 等. 南海北部大陆架东区台西南盆地石油地质特征与勘探前景分析[J]. 天然气地球科学, 2006, 17(3): 345−350. He Jiaxiong, Xia Bin, Wang Zhixin, et al. Petroleum geologic characteristics and exploration base of Taixinan Basin in eastern area of continental shelf in northern of the South China Sea[J]. Natural Gas Geoscience, 2006, 17(3): 345−350.
[53]	苏丕波, 何家雄, 梁金强, 等. 南海北部陆坡深水区天然气水合物成藏系统及其控制因素[J]. 海洋地质前沿, 2017, 33(7): 1−10. Su Pibo, He Jiaxiong, Liang Jinqiang, et al. Natural gas hydrate migration and accumulation system and its controlling factors on northern deep water slope of the South China Sea[J]. Marine Geology Frontiers, 2017, 33(7): 1−10.
[54]	苏丕波, 梁金强, 沙志彬, 等. 神狐深水海域天然气水合物成藏的气源条件[J]. 西南石油大学学报(自然科学版), 2014, 36(2): 1−8. Su Pibo, Liang Jinqiang, Sha Zhibin, et al. Gas sources condition of gas hydrate Formation in Shenhu deep water sea zone[J]. Journal of Southwest Petroleum University (Science & Technology Edition), 2014, 36(2): 1−8.
[55]	黄伟, 张伟, 梁金强, 等. 琼东南盆地和郁陵盆地天然气水合物成藏对比研究[J]. 中国矿业大学学报, 2021, 50(2): 363−380. Huang Wei, Zhang Wei, Liang Jinqiang, et al. Comparative study of gas hydrate accumulation system in the Qiongdongnan Basin of the South China Sea and the Ulleung Basin of Korea[J]. Journal of China University of Mining & Technology, 2021, 50(2): 363−380.
[56]	Kennett J P, Cannariato K G, Hendy I L, et al. Methane Hydrates in Quaternary Climate Change: the Clathrate Gun Hypothesis[M]. Washington: American Geophysical Union, 2003.
[57]	Paull C K, Buelow W J, Ussler III W, et al. Increased continental-margin slumping frequency during sea-level lowstands above gas hydrate-bearing sediments[J]. Geology, 1996, 24(2): 143−146. doi: 10.1130/0091-7613(1996)024<0143:ICMSFD>2.3.CO;2
[58]	何家雄, 万志峰, 张伟, 等. 南海北部泥底辟/泥火山形成演化与油气及水合物成藏[M]. 北京: 科学出版社, 2019. He Jiaxiong, Wan Zhifeng, Zhang Wei, et al. Formation and Evolution of Mud Diapir/Mud Volcano and Hydrocarbon and Hydrate Accumulation in Northern South China Sea[M]. Beijing: Science Press, 2019.
[59]	Crutchley G J, Mountjoy J J, Pecher I A, et al. Submarine slope instabilities coincident with shallow gas hydrate systems: insights from New Zealand examples[M]//Lamarche G, Mountjoy J, Bull S, et al. Submarine Mass Movements and their Consequences. Cham: Springer, 2016: 401−409.
[60]	张丙坤, 李三忠, 夏真, 等. 南海北部海底滑坡与天然气水合物形成与分解的时序性[J]. 大地构造与成矿学, 2014, 38(2): 434−440. Zhang Bingkun, Li Sanzhong, Xia Zhen, et al. Time sequence of submarine landslides and gas hydrates in the northern South China Sea[J]. Geotectonica et Metallogenia, 2014, 38(2): 434−440.
[61]	周吉林, 王秀娟, 朱振宇, 等. 海底滑坡对天然气水合物和游离气分布及富集的影响[J]. 地球物理学报, 2022, 65(9): 3674−3689. Zhou Jilin, Wang Xiujuan, Zhu Zhenyu, et al. The influence of submarine landslides on the distribution and enrichment of gas hydrate and free gas[J]. Chinese Journal of Geophysics, 2022, 65(9): 3674−3689.