Fluid migration and seabed methane seepage associated with marine gas hydrate systems

doi:10.13745/j.esf.sf.2024.6.54

Abstract

Abstract:

It is crucial for comprehending the accumulation mechanisms of gas hydrates and assessing the potential environmental impacts caused by their dissociation and associated methane seepage to understand fluid migration processes and seabed methane seepage in gas hydrate studies. This paper analyzes the relationships between fluid migration conduits, seabed methane seepage, and gas hydrate systems by examining numerous gas hydrate case studies worldwide. Fluid migration conduits are categorized into two types based on their roles in the gas hydrate system. Type I conduits are primarily distributed below the bottom simulating reflector (BSR) and serve as gas sources for the gas hydrate system. Type II conduits are in sediments above the BSR and may extend to the seabed, acting as pathways for gas leakage from the gas hydrate system. The role of polygonal faults as fluid migration conduits is considered limited, mainly contributing to the accumulation of shallow gas and gas hydrates. Seabed methane seepage is classified into three categories and five subcategories based on the spatial relationship between methane seepage, the gas hydrate system, and gas source conditions: (1) Deeper than the landward limit of the gas hydrate stability zone (LLGHSZ): (Hydrate-related gas source and non-hydrate-related gas source); (2) Around the LLGHSZ (Hydrate-related gas source and non-hydrate-related gas source); (3) Shallower than the LLGHSZ (Non-hydrate-related gas source). The intensity and density of methane leakage are highest near the LLGHSZ. This classification of fluid migration conduits and seabed methane seepage provides a framework for understanding the dynamic processes of gas hydrate accumulation and dissociation. It also offers insights into evaluating the environmental and climatic impacts associated with gas hydrate systems.

Key words: gas hydrates, BSR, landward limit, fluid migration, seabed methane seepage

CLC Number:

P738
P631

YANG Jinxiu, WANG Chen, XING Lanchang, WEI Wei, ZHANG Wei, HAN Weifeng, ZHAO Li, LIU Kunyi. Fluid migration and seabed methane seepage associated with marine gas hydrate systems[J]. Earth Science Frontiers, 2025, 32(2): 113-125.

Figures/Tables 10

References 74

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工区位置	LLGHSZ 深度/m	相关甲烷渗透特征	CH₄通量	诱发机制	参考文献
Rio Grande Cone (RGC) of SE Brazil	515	麻坑、自生碳酸盐	100 mmol m^-2·a^-1	海洋变暖	[4]
US Atlantic margin	505	自生碳酸盐、深水珊瑚、羽状流	/	中层水持续升温、地层侵蚀	[19]
Continental margin of West Spitsbergen	400	羽状流	/	向北流动的西斯匹次卑尔根的暖流	[20]
Offshore Western Svalbard	360~410	羽状流、有孔虫δ¹³C值偏负	30,550 mmol m^-2·a^-1	海洋变暖	[16⇓-18]
Arctic Ocean	290	自生碳酸盐	区域上BSR下移20 m, 释放100 Gt C	海洋变暖	[3]
Continental slopes of the Black Sea	200~300	麻坑	/	海洋变暖	[21]

工区位置	LLGHSZ 深度/m	相关甲烷渗透特征	CH₄通量	诱发机制	参考文献
Rio Grande Cone (RGC) of SE Brazil	515	麻坑、自生碳酸盐	100 mmol m^-2·a^-1	海洋变暖	[4]
US Atlantic margin	505	自生碳酸盐、深水珊瑚、羽状流	/	中层水持续升温、地层侵蚀	[19]
Continental margin of West Spitsbergen	400	羽状流	/	向北流动的西斯匹次卑尔根的暖流	[20]
Offshore Western Svalbard	360~410	羽状流、有孔虫δ¹³C值偏负	30,550 mmol m^-2·a^-1	海洋变暖	[16⇓-18]
Arctic Ocean	290	自生碳酸盐	区域上BSR下移20 m, 释放100 Gt C	海洋变暖	[3]
Continental slopes of the Black Sea	200~300	麻坑	/	海洋变暖	[21]

工区位置	BSR深度/ (TWT s^-1)	水合物系统	相关通道	GHL位置	参考文献
Offshore Mauritania	3.0~0.88	BSR,GHL,FGZ	断层、底辟	位于GHSZ底界之上	[34]
Niger Delta	3.6~3.2	BSR,GHL,GZ	断层、气烟囱	位于GHSZ内部	[35]
Qiongdongnan Basin	2.5~2.0	BSR	气烟囱		[12]
Active Margins off SW Taiwan	2.4~2.0	BSR,GHL,FGZ	气烟囱、渗透性砂岩层	位于GHSZ底界之上	[36]
LW3 Area: The Northern Slope of the South China Sea	2.0~1.9	BSR,GHL,FGZ	断层	位于GHSZ底界之上	[37]
Krishna-Godavari Basin	3.13~2.75	BSR,GHL,FGZ	渗透性砂岩层	位于GHSZ内部	[38]
Shenhu area in South China Sea	2.1~1.9	BSR,FGZ	泥底辟、气烟囱、渗透性砂岩层		[39-40]
Porangahau Ridge	3.6~3.4	BSR,GHL,FGZ	渗透性砂岩层	位于GHSZ内部	[41]
Offshore Colombia	2.5~1.5	BSR,FGZ	断层、渗透性砂岩层		[42]
Eastern South Korea Plateau (ESKP),East Sea	1.4~1.0	BSR,GHL,FGZ	气烟囱、渗透性砂岩层	位于GHSZ底界之上	[43]
Fiordland margin SW	2.9~1.2	BSR,GHL	无	位于GHSZ底界之上	[44]
Northern deep-water Gulf of Mexico	2.42~1.74	BSR,GHL,FGZ	断层、渗透性砂岩层	位于GHSZ底界之上	[45]
Svyatogor Ridge	2.25~2.20	BSR,GHL,FGZ	断层、气烟囱	位于GHSZ底界之上、位于GHSZ内部	[46]
Cameroon margin,offshore West Africa	2.5~1.9	BSR,FGZ	断层、气烟囱		[47]
Southern Hikurangi margin (New Zealand)	1.15~0.90	BSR,GHL,FGZ	渗透性砂岩层	GHL位于BSR上部、位于GHSZ内部,高于BSR	[48]
Northwestern Sea of Okhotsk	1.0~0.6	BSR,FGZ	泥底辟、气烟囱、断层		[49]
Eastern margin of the Sea of Japan	1.7~1.5	BSR,GHL,FGZ	气烟囱、断层	位于GHSZ内部,高于BSR	[50]
Offshore Oregon	1.3~1.2	BSR,GHL,FGZ	气烟囱、断层、渗透性砂岩层	位于GHSZ内部,高于BSR	[51]
Chilean margin offshore of Valdivia (40°S)	4.38~2.5	BSR,GHL,FGZ	断层	含水合物层位于BSR上部、位于GHSZ内部,高于BSR	[52]
Offshore mid-Norway	1.8~1.5	BSR,GHL	无	位于GHSZ底界之上	[53]

工区位置	BSR深度/ (TWT s^-1)	水合物系统	相关通道	GHL位置	参考文献
Offshore Mauritania	3.0~0.88	BSR,GHL,FGZ	断层、底辟	位于GHSZ底界之上	[34]
Niger Delta	3.6~3.2	BSR,GHL,GZ	断层、气烟囱	位于GHSZ内部	[35]
Qiongdongnan Basin	2.5~2.0	BSR	气烟囱		[12]
Active Margins off SW Taiwan	2.4~2.0	BSR,GHL,FGZ	气烟囱、渗透性砂岩层	位于GHSZ底界之上	[36]
LW3 Area: The Northern Slope of the South China Sea	2.0~1.9	BSR,GHL,FGZ	断层	位于GHSZ底界之上	[37]
Krishna-Godavari Basin	3.13~2.75	BSR,GHL,FGZ	渗透性砂岩层	位于GHSZ内部	[38]
Shenhu area in South China Sea	2.1~1.9	BSR,FGZ	泥底辟、气烟囱、渗透性砂岩层		[39-40]
Porangahau Ridge	3.6~3.4	BSR,GHL,FGZ	渗透性砂岩层	位于GHSZ内部	[41]
Offshore Colombia	2.5~1.5	BSR,FGZ	断层、渗透性砂岩层		[42]
Eastern South Korea Plateau (ESKP),East Sea	1.4~1.0	BSR,GHL,FGZ	气烟囱、渗透性砂岩层	位于GHSZ底界之上	[43]
Fiordland margin SW	2.9~1.2	BSR,GHL	无	位于GHSZ底界之上	[44]
Northern deep-water Gulf of Mexico	2.42~1.74	BSR,GHL,FGZ	断层、渗透性砂岩层	位于GHSZ底界之上	[45]
Svyatogor Ridge	2.25~2.20	BSR,GHL,FGZ	断层、气烟囱	位于GHSZ底界之上、位于GHSZ内部	[46]
Cameroon margin,offshore West Africa	2.5~1.9	BSR,FGZ	断层、气烟囱		[47]
Southern Hikurangi margin (New Zealand)	1.15~0.90	BSR,GHL,FGZ	渗透性砂岩层	GHL位于BSR上部、位于GHSZ内部,高于BSR	[48]
Northwestern Sea of Okhotsk	1.0~0.6	BSR,FGZ	泥底辟、气烟囱、断层		[49]
Eastern margin of the Sea of Japan	1.7~1.5	BSR,GHL,FGZ	气烟囱、断层	位于GHSZ内部,高于BSR	[50]
Offshore Oregon	1.3~1.2	BSR,GHL,FGZ	气烟囱、断层、渗透性砂岩层	位于GHSZ内部,高于BSR	[51]
Chilean margin offshore of Valdivia (40°S)	4.38~2.5	BSR,GHL,FGZ	断层	含水合物层位于BSR上部、位于GHSZ内部,高于BSR	[52]
Offshore mid-Norway	1.8~1.5	BSR,GHL	无	位于GHSZ底界之上	[53]