Origin and genetic mechanism of hydrocarbon gas sources of the highly saturated gas hydrate deposits in the northern South China Sea

被引：0

作者：

Lai, Hongfei ^{[1
]}

Kuang, Zenggui ^{[1
]}

Fang, Yunxin ^{[1
]}

Xu, Chenlu ^{[1
]}

Ren, Jinfeng ^{[1
]}

Liang, Jinqiang ^{[1
]}

Lu, Jing'an ^{[1
]}

机构：

[1] National Engineering Research Center of Gas Hydrate Exploration and Development, Guangzhou Marine Geological Survey, Guangzhou

来源：

Earth Science Frontiers | 2025年 / 32卷 / 02期

关键词：

accumulation mechanism; gas origin; hydrate gas supply system; natural gas hydrate; secondary microbial gas;

D O I：

10.13745/j.esf.sf.2024.6.53

中图分类号：

学科分类号：

摘要：

The origin of hydrocarbon gas is crucial for clarifying the formation and accumulation mechanisms of natural gas hydrate. Many highly saturated natural gas hydrate deposits have been drilled in the northern South China Sea. However, the source and genetic mechanism of hydrocarbon gases have not been systematically elucidated, significantly restricting the identification of main gas sources and the deployment of future exploration strategies. In this study, taking the typical highly saturated gas hydrate deposits in the Qiongdongnan and Shenhu areas as examples, the source and genetic mechanism of hydrocarbon gases are systematically investigated using an integrated approach that includes gas geochemistry, Sediment organic geochemistry, geomicrobiology, and seismic interpretation. The results show that the genetic types of hydrate gases in the northern South China Sea are diverse, including primary and secondary microbial gases, as well as thermogenic coal-type and oil-type gases. Notably, the thermogenic gases within different gas hydrate deposits have undergone microbial degradation and modification to varying extents: Shenhu Wll-17 gas hydrate deposit>Shenhu W18-19 gas hydrate deposit>Qiongdongnan GMGS5-W08 gas hydrate deposit. The hydrate gas source layer consists of a shallowly buried microbial gas source layer (20~85 C) and a deeply buried thermogenic gas source layer (vitrinite reflectance Ro>0. 5%). The upper part of the microbial gas source layer (<300 mbsf), which has been drilled and sampled, shows relatively low gas generative potential. In contrast, the thermogenic gas source represents great gas generative potential due to the existence of effective source kitchens and gas-prone coal-type source rocks in the mature stage. The deeply buried thermogenic source kitchen, conventional hydrocarbon deposits, shallowly buried microbial gas source layer, and composite gas migration conduits (including depression-controlled faults, gas chimneys, tubulär seeps, and microfractures) constitute the hydrocarbon gas supply System for the highly saturated gas hydrate deposits in the northern South China Sea. The contribution of the deeply buried thermogenic source kitchen is extremely critical for the large-scale accumulation of gas hydrate. However, most of the thermogenic gases transported through the microbial gas source layer undergo severe microbial degradation and are ultimately converted into secondary microbial methane for gas hydrate mineralization. There are three major pathways for hydrocarbon gases in the highly saturated hydrate deposits of the northern South China Sea:(l) Hydrate gases directly originating from the deeply buried thermogenic gas source kitchen, i.e.. non-biodegraded thermogenic gas. (2)Hydrate gases derived from secondary microbial gases, which are generated by anaerobic methanogenesis degradation processes after deeply buried thermogenic hydrocarbons migrate into the microbial gas source layer. (3) Hydrate gases supplied by primary microbial gases, which are generated by microbial utilization of in-situ sediment organic matter in the shallowly buried microbial gas source layer. © 2025 Science Frontiers editorial department. All rights reserved.

引用

页码：36 / 60

页数：24

共 53 条

[1]

COLLETT T S., JOHNSON A H, KNAPP C C., Et al., Natural gas hydrates: a review, Natural gas hydrates: energy re-source potential and associated geologic hazards, pp. 146-219, (2009)

[2]

COLLETT T S., Energy resource potential of natural gas hy-drates, American Association of Petroleum Geologists Bulletin, 86, 11, pp. 1971-1992, (2002)

[3]

KVENVOLDEN K A., The global occurrence of natural gas hydrates, Natural Gas Hydrates Occurrence Distribution & Detection, pp. 3-18, (2001)

[4]

COLLETT T S., BOSWELL R, WAITE W F, Et al., India national gas hydrate program expedition 02 summary of scientific results: gas hydrate Systems along the eastern Continental margin of lndia, Marine and Petroleum Geology, 108, pp. 39-142, (2019)

[5]

SASSEN R., LOSH S L, CATHLES 111 L., Et al., Massive vein-filling gas hydrate: relation to ongoing gas migration from the deep subsurface in the Gulf of Mexico[J], Marine and Petroleum Geology, 18, 5, pp. 551-560, (2001)

[6]

YE J L., WEI J G, LIANG J Q, Et al., Complex gas hydrate System in a gas chimney, South China Sea[J], Marine and Petroleum Geology, 104, pp. 29-39, (2019)

[7]

ZHANG G X, LIANG J Q, LU J A, Et al., Geological fea-tures, Controlling factors and potential prospects of the gas hydrate occurrence in the east part of the Pearl River Mouth Basin, South China Sea, Marine and Petroleum Geology, 67, pp. 356-367, (2015)

[8]

MENG M M, LIANG J Q, LU J A, Et al., Quaternary deep-water sedimentary characteristics and their relationship with the gas hydrate accumulations in the Qiongdongnan Basin, Northwest South China Sea, Deep Sea Research Part I: Oceanographic Research Papers, 177, (2021)

[9]

ZHANG W, LIANG J Q, WEI J G, Et al., Geological and geophysical features of and controls on occurrence and accu-mulation of gas hydrates in the first offshore gas-hydrate production test region in the Shenhu area, northern South China Sea, Marine and Petroleum Geology, 114, (2020)

[10]

WANG X J, COLLETT T S, LEE M W, Et al., Geological controls on the occurrence of gas hydrate from core, down-hole log, and seismic data in the Shenhu area, South China Sea, Marine Geology, 357, pp. 272-292, (2014)

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