Geochemical characteristics of cold-seep carbonates in Shenhu area, South China Sea

Chong-min, Chen; Zhong, Ling; Wan, Zhifeng; Cheng, Chiyu; Zhou, Wei; Xu, Xinliang

doi:10.1007/s00343-021-1112-z

Cited by 3 publications

(1 citation statement)

References 94 publications

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“…A biogeochemical study has indicated that the carbonate phase in the surface sediment from Haima is predominantly high-Mg calcite, suggesting high methane fluxes, and significant AOM activity in the area (Liu et al, 2020). The carbonate minerals at Haima are mainly aragonite, calcite, and lesser amounts of dolomite, which vary greatly in mineral composition (Chen et al, 2022a). These studies have revealed the role of geochemical factors of cold seeps in driving changes in microbial communities and mineral composition.…”

Section: Introductionmentioning

confidence: 94%

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Liang,

Feng,

Kong

et al. 2023

Front. Mar. Sci.

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Cold seeps create diverse habitats in the deep sea and play an important role in the global carbon cycling. Anaerobic oxidation of methane (AOM) and biogenic mineralization are essential carbon pathways of methane and carbon transformation in cold seeps, however, the effects of habitat heterogeneity on the processes are still poorly understood. In this study, we investigated the microbial communities and mineral assemblages at distinct habitats in the Haima cold seep and their relationships with environmental factors. These habitats were classified as methane seep site (MS), seep-free faunal habitat (FH), and control site (CS). Bacterial communities were significantly different among the three habitats. ANME-3 archaea, Sulfurovum bacteria, and mineralization-associated microbes (e.g., Campylobacterales) were detected in high relative abundances at ROV2. Mineralogical analysis revealed abundant calcite minerals at the seep site, indicating that authigenic carbonate minerals were formed at highly active seep. Multivariate statistical analysis demonstrated that the concentrations of SO42–, Ca2+, and Mg2+ were significantly correlated with the presence of calcite minerals and bacterial communities. These results suggested that AOM-accompanied authigenic carbonate formation is an important factor influencing the mineral assemblages in seep habitats. This finding improves our understanding of marine microbial carbon cycling.

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Section: Introductionmentioning

confidence: 94%

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Liang,

Feng,

Kong

et al. 2023

Front. Mar. Sci.

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Source-Reservoir Characteristics and Accumulation of Gas Chimney-Type Gas Hydrates in Qiongdongnan Basin, Northern South China Sea

Fan

Zhou

et al. 2022

Front. Earth Sci.

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The Qiongdongnan Basin is an important gas hydrate exploration area in the South China Sea, but the gas hydrate accumulation process is poorly understood. By selecting an Lingshui (LS) target area and using first-hand geochemical data, three-dimensional seismic data, and an independent thermal insulation and pressure maintaining shipborne core analysis system, in this study, comprehensive geological evaluation was carefully conducted around the gas source and reservoir of the gas chimney hydrates, and the accumulation process was investigated. Geochemical data for a total of 47 sets of gas samples revealed that the gas source of the hydrates in the study area was mainly thermogenic gas supplemented by mixed gas. It was predicted that the contribution of the thermogenic gas to the hydrate accumulation was up to 70%. Using the independent shipborne core analysis system, the characteristics of the low-temperature combustible gas hydrates were determined, and the reservoir in the study area was characterized as non-diagenetic to weakly diagenetic, rich in clay and silt (D50 = 15.1–34.1 μm), weakly self-sustaining, and strongly heterogeneous. Based on the differentiated seismic response of the hydrate layer-gas bearing hydrate layer-shallow gas layer at the top of the gas chimney, the accumulation process in the target area was determined to be as follows: remote thermogenic gas transportation, local microbial genetic gas accumulation, episodic dynamic gas chimney reservoir formation, and source-reservoir control. In addition, the exploration ideas of an effective supply from a gas source and a shallow large-scale sand body are emphasized. The results of this study provide an important reference for the trial production of natural gas hydrates in the South China Sea.

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Gas production characteristics of biogenic gas simulated in hydrate-developing area of Dongsha area, South China Sea

Wei

Shi

et al. 2023

Front. Mar. Sci.

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Most of the natural gas hydrate sources in the world are biogenic gas, but there are still many unsolved problems in the formation process of biogenic gas. The gas source of gas hydrates in the northern South China Sea is also controversial, and the evaluation of biogas source rock in hydrate development areas lacks experimental basis and quantitative data. In order to solve these problems, this paper used the sediments obtained from the GMGS2 hydrate drilling voyage to simulate the biological gas production. Through the culture experiment, the relationship between sedimentary gas production, temperature and sediment characteristics in the hydrate development area of Dongsha Sea area was comparatively studied, and the results were compared with typical biological gas fields. The results showed that CH4 and CO2 were the main gas products, and a small amount of H2 was formed. Methane yield is closely related to temperature, and the optimal temperature range in the study area is 20°C~ 40°C. At the same time, it is found that organic carbon content (TOC) has no significant correlation with methane yield, and it is not suitable to be used as an index for the evaluation of biogas source rock. Comprehensive analysis shows that the methane production rate in the study area is relatively high and the hydrocarbon generation potential is great, which meets the gas source conditions for the formation of gas hydrate ore body. The main factors affecting biomethane yield include available organic matter, bacterial community and environmental factors.

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Geochemical characteristics of cold-seep carbonates in Shenhu area, South China Sea

Cited by 3 publications

References 94 publications

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Microbial communities and mineral assemblages in sediments from various habitats at the Haima Cold Seep, South China Sea

Source-Reservoir Characteristics and Accumulation of Gas Chimney-Type Gas Hydrates in Qiongdongnan Basin, Northern South China Sea

Gas production characteristics of biogenic gas simulated in hydrate-developing area of Dongsha area, South China Sea

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