The Seismic Facies in the Pliocene from the Shenhu Gas Hydrate Survey in the Northern Continental Slope of South China Sea

According to the tectonic movement occurring in the South China Sea since the late Miocene and the sea level changes in Yingqiong Basin, Pearl River Mouth Basin, and global, combining with seismic reflection terminate characteristics, we divided Shenhu gas hydrate survey areas Pliocene strata into four sequences. According to the basic principles of the "outside-shape, internal-structure ,from seismic wave external geometry, supplemented by seismic physical attributes (amplitude, frequency, consistence),we identified the fill, mound, sheet, lens, sheet shape, wedge-shaped 6 categories, a total of 19 kinds of seismic facies in the study area. Contrasting to the drilling gas hydrate depth, the gas hydrate is mainly enriched around the slump deposits.

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Sequence architecture and depositional evolution of Eocene to Oligocene, synrift to early postrift strata in the Baiyun Sag, South China Sea

Interpretation ◽

10.1190/int-2018-0055.1 ◽

2019 ◽

Vol 7 (2) ◽

pp. T309-T329

Author(s):

Nanan Gao ◽

Changsong Lin ◽

Kenneth Eriksson ◽

Zhongtao Zhang ◽

Da Gao ◽

...

Keyword(s):

South China Sea ◽

South China ◽

River Mouth ◽

Passive Margin ◽

Seismic Facies ◽

Pearl River Mouth Basin ◽

China Sea ◽

Baiyun Sag ◽

Shelf Slope ◽

Depositional Evolution

The Pearl River Mouth Basin (PRMB), located on the northern continental margin of the South China Sea, underwent a complex evolution during the Paleogene. We have focused on the Baiyun Sag in the PRMB with the goal of constructing the architecture and depositional evolution of the Eocene–Early Oligocene synrift stage to the Late Oligocene early postrift stage of basin evolution. Based on analysis of 3D seismic data complemented by well logs and cores, the Paleogene basin fills can be classified into three composite sequences bounded by regional unconformities and 14 sequences bounded by local unconformities. We identify seismic facies on the basis of different internal reflection configurations, external shapes, and contact relationships. The distribution of seismic facies and lithologies interpreted from gamma-ray curves reveal that the synrift basin fill consists mainly of fan delta deposits adjacent to the southern fault scarp, braid delta deposits on the adjacent hanging-wall blocks, and lacustrine mudstones and sublacustrine fan deposits in the center of the basin. The overlying early postrift stage is dominated by shelf and shelf-slope environments, with widespread developed southward-prograding deltas and submarine fans. Tectonics is the principal controlling factor on the development and distribution of depositional systems during the synrift stage. In contrast, sea-level changes superimposed on long-term subsidence related to thermal cooling determined the stacking patterns of sequences during the postrift stage. The results provide new insights on synrift and early postrift tectonics and sedimentation patterns along an evolving passive margin.

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Production performance of gas hydrate accumulation at the GMGS2-Site 16 of the Pearl River Mouth Basin in the South China Sea

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2015.08.071 ◽

2015 ◽

Vol 27 ◽

pp. 306-320 ◽

Cited By ~ 27

Author(s):

Jing-Chun Feng ◽

Yi Wang ◽

Xiao-Sen Li ◽

Gang Li ◽

Yu Zhang ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Gas Hydrate ◽

River Mouth ◽

The South China Sea ◽

Production Performance ◽

Pearl River ◽

Pearl River Mouth Basin ◽

China Sea ◽

The Pearl River

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Gas Hydrate System of Shenhu Area, Northern South China Sea: Geochemical Results

Journal of Geological Research ◽

10.1155/2011/370298 ◽

2011 ◽

Vol 2011 ◽

pp. 1-10 ◽

Cited By ~ 20

Author(s):

Nengyou Wu ◽

Haiqi Zhang ◽

Shengxiong Yang ◽

Guangxue Zhang ◽

Jinqiang Liang ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Gas Hydrate ◽

Northern South China Sea ◽

River Mouth ◽

Geochemical Data ◽

Pearl River Mouth Basin ◽

Silty Clay ◽

Shenhu Area ◽

China Sea

The drilling recovered high-concentration methane hydrates (maximum 26–48%) in a disseminated form in silty clay sediments in Shenhu area of Pearl River Mouth Basin, South China Sea. Combining the geochemical data, the gas hydrate-bearing sediments are 10 m to 43 m in thickness and located just above the base of the gas hydrate stability zone. The methane content is 96.10–99.91% with small amount of ethane and propane. The baseline chlorinity of pore waters shows 10% lower than that of shallow sediments below and inside the gas hydrate zone. The methane/ethane ratios are higher than 1000 above the gas hydrate zone and less than 1000 at the interval of gas hydrate zone. The depth of sulphate methane interface varies from site to site as 17 to 27 mbsf. These results show that the methane of gas hydrate was mainly originated from microbial activity and the upward methane flux is minor. This is evidenced by the δC13CH4 values of headspace gases from the gravity piston cores and released gases from pressure cores, which range from −74.3‰ PDB to −46.2‰ PDB, with the majority less than −55%‰ PDB. The hydrate deposit is a distributed gas hydrate system in Shenhu area.

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