SCSIO OpenIR  > 中科院边缘海地质重点实验室
Types, Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea
Su, M; Sha, ZB; Zhang, CM; Wang, HB; Wu, NY; Yang, R; Liang, JQ; Qiao, SH; Cong, XR; Liu, J; suming@ms.giec.ac.cn; shazb2008@163.com
2017
Source PublicationACTA GEOLOGICA SINICA-ENGLISH EDITION
Volume91Issue:1Pages:219-231
AbstractThe first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T conditions, geophysical anomalies and saturation calculations of these gas hydrates, but has not documented in detail the migration of gas-bearing fluids in the study area. Based on the interpretations of 2D/3D seismic data, this work identified two types of migration pathways for gas-bearing fluids in the Shenhu area, i.e., vertical and lateral pathways. The vertical pathways (large-scale faults, gas chimneys and mud diapirs) presented as steep seismic reflection anomalies, which could be traced downward to the Eocene source rocks and may penetrate into the Late Miocene strata. The deeper gases/fluids might be allowed migrating into the shallower strata through these vertical conduits. However, the distributions showed distinct differences between these pathways. Large-scale faults developed only in the north and northeast of the Shenhu area, while in the drilling area gas chimneys were the sole vertical migration pathways. Since the Pliocene, normal faults, detachment faults and favorable sediments have constituted the lateral pathways in the Shenhu gas hydrate drilling area. Although these lateral pathways were connected with gas chimneys, they exerted different effects on hydrate formation and accumulation. Gas-bearing fluids migrated upward along gas chimneys might further migrate laterally because of the normal faults, thereby enlarging the range of the chimneys. Linking gas chimneys with the seafloor, the detachment faults might act as conduits for escaping gases/fluids. Re-deposited sediments developed at the early stage of the Quaternary were located within the gas hydrate stability zone, so hydrates would be enriched in these favorable sediments. Compared with the migration pathways (large-scale faults and mud diapirs) in the LW3-1 deep-sea oil/gas field, the migration efficiency of the vertical pathways (composed of gas chimneys) in the gas hydrate drilling area might be relatively low. Description and qualitative discrimination of migration pathways in the Shenhu gas hydrate drilling area are helpful to further understand the relationship between good-quality deep source rocks and shallow, mainly biogenically-produced, hydrates. As the main source rocks of the Baiyun sag, lacustrine mudstones in the Wenchang and Enping Formations may provide thermogenic methane. Gas chimneys with relatively low migration efficiency created the vertical pathways. Caused by the Dongsha tectonic movement, the release of overpressured fluids might reduce the vertical migration rates of the thermogenic methane. The thick bathyal/abyssal fine-grained sediments since the Late Miocene provided migration media with low permeability. These preconditions may cause carbon isotopic fractionation of thermogenic methane during long-distance vertical migrations. Therefore, although geochemical analyses indicate that the methane forming gas hydrate in the Shenhu area was mainly produced biogenically, or was mixed methane primarily of microbial origin, thermogenic methane still contribute significantly.
Department[Su, Ming; Yang, Rui; Qiao, Shaohua; Cong, Xiaorong; Liu, Jie] Chinese Acad Sci, Key Lab Gas Hydrate, Guangzhou 510640, Guangdong, Peoples R China; [Su, Ming; Yang, Rui; Qiao, Shaohua; Cong, Xiaorong; Liu, Jie] Guangzhou Key Lab New & Renewable Energy Res & De, Guangzhou 510640, Guangdong, Peoples R China; [Su, Ming; Yang, Rui; Qiao, Shaohua; Cong, Xiaorong; Liu, Jie] Chinese Acad Sci, Guangzhou Inst Energy Convers, Guangzhou 510301, Guangdong, Peoples R China; [Sha, Zhibin; Wang, Hongbin; Liang, Jinqiang] Guangzhou Marine Geol Survey, Guangzhou 510075, Guangdong, Peoples R China; [Zhang, Cuimei] Chinese Acad Sci, South China Sea Inst Oceanol, Key Lab Marginal Sea Geol, Guangzhou 510301, Guangdong, Peoples R China; [Wu, Nengyou] Minist Land & Resources, Key Lab Gas Hydrate, Qingdao 266071, Shandong, Peoples R China
KeywordMigrating Pathways Gas-bearing Fluids Gas Hydrates Shenhu Area NorThern Continental Slope Of The South China Sea
Funding ProjectMSG
Document Type期刊论文
Identifierhttp://ir.scsio.ac.cn/handle/344004/16476
Collection中科院边缘海地质重点实验室
Corresponding Authorsuming@ms.giec.ac.cn; shazb2008@163.com
Recommended Citation
GB/T 7714
Su, M,Sha, ZB,Zhang, CM,et al. Types, Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea[J]. ACTA GEOLOGICA SINICA-ENGLISH EDITION,2017,91(1):219-231.
APA Su, M.,Sha, ZB.,Zhang, CM.,Wang, HB.,Wu, NY.,...&shazb2008@163.com.(2017).Types, Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea.ACTA GEOLOGICA SINICA-ENGLISH EDITION,91(1),219-231.
MLA Su, M,et al."Types, Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea".ACTA GEOLOGICA SINICA-ENGLISH EDITION 91.1(2017):219-231.
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