Differential Scanning Calorimetry Research of Hydrates Phase Equilibrium in Porous Media

2012 ◽  
Vol 512-515 ◽  
pp. 2122-2126
Author(s):  
Qiang Chen ◽  
Chang Ling Liu ◽  
Yu Guang Ye
Keyword(s):  
Differential Scanning Calorimetry ◽  
Porous Media ◽  
Phase Equilibrium ◽  
South China Sea ◽  
Pore Water ◽  
South China ◽  
Pure Water ◽  
Scanning Calorimetry ◽  
Equilibrium Conditions ◽  
China Sea

In this paper, we focused on the determination of phase equilibrium conditions of hydrates formed in the pore water and porous media from South China Sea. High pressure differential scanning calorimetry (HP DSC), a relatively new thermo-analytical technique was applied to this research. During the study, nitrogen hydrates and methane hydrates phase equilibrium conditions were determined in thewater-hydrates- gas (W-H-G) system. Then a series of experiments were carried on using core sample drilled from South China Sea to determine the phase equilibrium properties in pore water and porous media systems. It show that the hydrates phase equilibrium point is about 2K lower than in pure water from pressure range 10 to 30 MPa, due to the thermodynamic inhibition effect of brine solution.

scholarly journals Environment-Dependent Distribution of the SedimentnifH-Harboring Microbiota in the Northern South China Sea

2012 ◽  
Vol 79 (1) ◽  
pp. 121-132 ◽  
Author(s):  
Hongyue Dang ◽  
Jinying Yang ◽  
Jing Li ◽  
Xiwu Luan ◽  
Yunbo Zhang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Community Structure ◽  
South China Sea ◽  
Pore Water ◽  
South China ◽  
Deep Sea ◽  
Methane Hydrate ◽  
Sediment Pore Water ◽  
China Sea ◽  
Biogeographical Distribution

ABSTRACTThe South China Sea (SCS), the largest marginal sea in the Western Pacific Ocean, is a huge oligotrophic water body with very limited influx of nitrogenous nutrients. This suggests that sediment microbial N2fixation plays an important role in the production of bioavailable nitrogen. To test the molecular underpinning of this hypothesis, the diversity, abundance, biogeographical distribution, and community structure of the sediment diazotrophic microbiota were investigated at 12 sampling sites, including estuarine, coastal, offshore, deep-sea, and methane hydrate reservoirs or their prospective areas by targetingnifHand some other functional biomarker genes. Diverse and novelnifHsequences were obtained, significantly extending the evolutionary complexity of extantnifHgenes. Statistical analyses indicate that sedimentin situtemperature is the most significant environmental factor influencing the abundance, community structure, and spatial distribution of the sedimentnifH-harboring microbial assemblages in the northern SCS (nSCS). The significantly positive correlation of the sediment pore water NH4+concentration with thenifHgene abundance suggests that the nSCS sedimentnifH-harboring microbiota is active in N2fixation and NH4+production. Several other environmental factors, including sediment pore water PO43−concentration, sediment organic carbon, nitrogen and phosphorus levels, etc., are also important in influencing the community structure, spatial distribution, or abundance of thenifH-harboring microbial assemblages. We also confirmed that thenifHgenes encoded by archaeal diazotrophs in the ANME-2c subgroup occur exclusively in the deep-sea methane seep areas, providing for the possibility to develop ANME-2cnifHgenes as a diagnostic tool for deep-sea methane hydrate reservoir discovery.

scholarly journals Early Diagenesis Records and Pore Water Composition of Methane-Seep Sediments from the Southeast Hainan Basin, South China Sea

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Daidai Wu ◽  
Nengyou Wu ◽  
Ying Ye ◽  
Mei Zhang ◽  
Lihua Liu ◽  
...  
Keyword(s):  
South China Sea ◽  
Pore Water ◽  
South China ◽  
Gas Hydrates ◽  
Cold Seep ◽  
Methane Seep ◽  
Gas Reservoirs ◽  
China Sea ◽  
Water Composition ◽  
Geochemical Properties

Several authigenic minerals were identified by XRD and SEM analyses in shallow sediments from the Southeast Hainan Basin, on the northern slope of South China Sea. These minerals include miscellaneous carbonates, sulphates, and framboidal pyrite, and this mineral assemblage indicates the existence of gas hydrates and a methane seep. The assemblage and fabric features of the minerals are similar to those identified in cold-seep sediments, which are thought to be related to microorganisms fostered by dissolved methane. Chemical composition of pore water shows that the concentrations of SO42-, Ca2+, Mg2+, and Sr2+ decrease clearly, and the ratios of Mg2+ to Ca2+ and Sr2+ to Ca2+ increase sharply with depth. These geochemical properties are similar to those where gas hydrates occur in the world. All results seem to indicate clearly the presence of gas hydrates or deep water oil (gas) reservoirs underneath the seafloor.

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