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1Geochemical characteristics of pore water in shallow sediments from Shenhu area of South China Sea and their significance for gas hydrate occurrence显示文摘The Shenhu area is one of the promise target areas for marine gas hydrate exploration in the northern margin of the South China Sea.Pore water samples were collected from two piston cores (8.75 and 8.52 m) in site HS-A and site HS-B in the Shenhu area,and their major anion and cation contents and trace element contents have been analyzed in this study.Cl- concentrations in pore waters are similar to the seawater value and no systematic change along depth profiles has been found for the Cl- content in both sites.In site HS-A,the SO 2- 4 contents show a limited range in pore waters from 0 to 3 m depths,but a dramatic decrease is documented in depth below 3 m.Other elements such as Ca 2+,Mg 2+ and Sr 2+ show similar variation patterns as the SO 2- 4,i.e.,no variation in 0-3 m,but large decrease in depth below 3 m.In site HS-B,both the SO 4 and Ca 2+,Mg 2+ and Sr 2+ display a decrease pattern along the depth profile,but in 0-3 m the variation is less significant than those in depth below 3 m.In both sites HS-A and HS-B,I contents show a dramatic increase along depth profiles.Calculations show that the SMI depths are very shallow (10 and 11 m) in both sites,and the sulfate flux and I flux are very high.These geochemical characteristics and anomalies at Shenhu are quite similar to those found in other gas hydrate locations in the world,and a genetic link is suggested to be related to the gas hydrate occurrence at depths in the study area.In summary,we suggest that combined geochemical parameters in shallow sediment pore waters are useful indicators to indicate the gas hydrate occurrence at depths.YANG Tao JIANG ShaoYong GE Lu YANG JingHong WU NengYou ZHANG GuangXue LIU Jian 2010Chinese Science Bulletin2010,55,8:30
2Types,Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area,Northern Continental Slope of the South China Sea显示文摘The 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(largescale 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 biogenicallyproduced, 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 ofthermogenic 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.SU Ming SHA Zhibin ZHANG Cuimei WANG Hongbin WU Nengyou YANG Rui LIANG Jinqiang QIAO Shaohua CONG Xiaorong LIU Jie 2017Acta Geologica Sinica(English Edition)2017,91,1:16
3Geochemistry of pore waters from HQ-1PC of the Qiongdongnan Basin, northern South China Sea, and its implications for gas hydrate exploration显示文摘The Qiongdongnan Basin is one of the target areas for marine gas hydrate exploration in the northern margin of the South China Sea. In this study, major anion (e.g., SO42 , Cl, Br, I), cation (e.g., Ca, Mg, K, Na), and trace element (e.g., Sr, Ba) con- centrations of pore water samples collected from site HQ-1PC in the Qiongdongnan Basin were analyzed. These geochemical data suggest that the process of AOM (Anaerobic Oxidation of Methane) is dominant in sulfate-reduction zone in this site due to high upwelling iodine flux and strong microbial activities. The iodine-rich fluids, which may carry methane for the gas hydrate formation, pass through the gas hydrate stability zone, mix with brine released during gas hydrate formation, and cause the geochemical anomalies observed at site HQ-1PC. The pore water geochemical characteristics and anomalies in the Qiongdongnan Basin are quite similar to those found in other gas hydrate locations in the Shenhu area in the northern South China Sea, and a genetic link is suggested with the possibility of gas hydrate occurrence in the study area.YANG Tao JIANG ShaoYong GE Lu YANG JingHong WU NengYou ZHANG GuangXue LIU Jian CHEN DaoHua 2013Science China Earth Sciences2013,56,4:14
4Characteristics of authigenic pyrites in shallow core sediments in the Shenhu area of the northern South China Sea: Implications for a possible mud volcano environment显示文摘Distinct pyrites have been recovered from a shallow sediment core from Site 4B in the Shenhu area of the northern South China Sea. Based on the lithology, texture and structure of sediments, the stable sulfur isotope of pyrite and the total organic carbon (TOC) concentration of the sediments, a distinctive sediment interface is identified at a depth of about 1 m below the seafloor in the core sediments. The pyrites only accumulate in the lower part of the core as rods and foraminifera-infillings, and mainly within three intervals marked by high pyrite concentrations. The amount of pyrite in the sediments shows no remarkable correlation with TOC in the Site 4B core sediments. The stable sulfur isotopes of the pyrite have extremely negative values ranging from 41.69‰ to 49.16‰. They are considered to be the mutual product of sulfate bacterial reduction and sulfur bacterial disproportionation. Our research proposes that Site 4B might be located in or near a possible mud volcano sedimentary environment; a large amount of methane could migrate from deep to shallow sediments in an active mud volcano and thereby play a key role in the intensity of sulfate bacterial reduction and the amount of pyrite formed at Site 4B. Further, the variation in flux of deep methane fluid by intermittent mud volcanic eruptions might result in the deposition of authigenic pyrite intervals.XIE Lei WANG JiaSheng WU NengYou WU DaiDai WANG Zhou ZHU XiaoWei HU Jun CHEN HongRen LIN Qi 2013Science China Earth Sciences2013,56,4:14
5Progress in Global Gas Hydrate Development and Production as a New Energy Resource显示文摘Natural gas hydrates have been hailed as a new and promising unconventional alternative energy,especially as fossil fuels approach depletion,energy consumption soars,and fossil fuel prices rise,owing to their extensive distribution,abundance,and high fuel efficiency.Gas hydrate reservoirs are similar to a storage cupboard in the global carbon cycle,containing most of the world's methane and accounting for a third of Earth's mobile organic carbon.We investigated gas hydrate stability zone burial depths from the viewpoint of conditions associated with stable existence of gas hydrates,such as temperature,pressure,and heat flow,based on related data collected by the global drilling programs.Hydrate-related areas are estimated using various biological,geochemical and geophysical tools.Based on a series of previous investigations,we cover the history and status of gas hydrate exploration in the USA,Japan,South Korea,India,Germany,the polar areas,and China.Then,we review the current techniques for hydrate exploration in a global scale.Additionally,we briefly review existing techniques for recovering methane from gas hydrates,including thermal stimulation,depressurization,chemical injection,and CH4-CO2 exchange,as well as corresponding global field trials in Russia,Japan,United States,Canada and China.In particular,unlike diagenetic gas hydrates in coarse sandy sediments in Japan and gravel sediments in the United States and Canada,most gas hydrates in the northem South China Sea are non-diagenetic and exist in fine-grained sediments with a vein-like morphology.Therefore,especially in terms of the offshore production test in gas hydrate reservoirs in the Shenhu area in the north slope of the South China Sea,Chinese scientists have proposed two unprecedented techniques that have been verified during the field trials:solid fluidization and formation fluid extraction.Herein,we introduce the two production techniques,as well as the so-called'fbur-in-one'environmental monitoring system employed during the Shenhu production test.Methane is not currently commercially produced from gas hydrates anywhere in the world;therefore,the objective of field trials is to prove whether existing techniques could be applied as feasible and economic production methods for gas hydrates in deep-water sediments and permafrost zones.Before achieving commercial methane recovery from gas hydrates,it should be necessary to measure the geologic properties of gas hydrate reservoirs to optimize and improve existing production techniques.Herein,we propose horizontal wells,multilateral wells,and cluster wells improved by the vertical and in dividual wells applied during existing field trials.It is noteworthy that relatively pure gas hydrates occur in seafloor mounds,within near-surface sediments,and in gas migration conduits.Their extensive distribution,high saturation,and easy access mean that these types of gas hydrate may attract considerable attention from academia and industry in the future.Herein,we also review the occurrence and development of concentrated shallow hydrate accumulations and briefly introduce exploration and production techniques.In the closing section,we discuss future research needs,key issues,and major challenges related to gas hydrate exploration and production.We believe this review article provides insight on past,present,and future gas hydrate exploration and production to provide guidelines and stimulate new work into the field of gas hydrates.LIU Liping SUN Zhilei ZHANG Lei WU Nengyou Yichao Qin JIANG Zuzhou GENG Wei CAO Hong ZHANG Xilin ZHAI Bin XU Cuiling SHEN Zhicong JIA Yonggang 2019Acta Geologica Sinica(English Edition)2019,93,3:13
6Undrained shear strength evaluation for hydrate-bearing sediment overlying strata in the Shenhu area, northern South China Sea显示文摘The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations.In situ piezocone penetration tests(CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China's first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments(HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays,the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays,while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.Yanlong Li Gaowei Hu Nengyou Wu Changling Liu Qiang Chen Chen'an Li 2019Acta Oceanologica Sinica2019,38,3:12
7Glycerol ether biomarkers and their carbon isotopic compositions in a cold seep carbonate chimney from the Shenhu area, northern South China Sea显示文摘At modern cold seeps,the anaerobic oxidation of methane(AOM)is the dominant pathway for methane consumption in marine sediments.AOM,which is mediated by a consortium of methane oxidizing archaea and sulfate reducing bacteria,is proposed to be responsible for authigenic carbonate formation.A methane-derived carbonate chimney was collected from the Shenhu area, northern South China Sea.The membrane lipids and their very low carbon isotopic compositions(?115‰to?104‰)in the Shenhu chimney suggest the presence of an AOM process.Three specific archaeal and bacterial biomarkers were detected,including Ar,DAGE 1f,and monocyclic MDGD.Their strongly depleted??13C values(?115‰to?104‰),which are lower than those of the normal marine lipids in sediments,reveal biogenic methane as their origin.The carbonate deposits exhibiting a chimney structure indicate that a vigorous methane-rich fluid expulsion may have occurred at the seafloor.We propose that the decomposition of gas hydrates at depth is the likely cause of seepage and cold seep carbonate formation in the Shenhu area.GE Lu JIANG ShaoYong YANG Tao YANG JingHong WU NengYou ZHANG GuangXue LIU Jian 2011Chinese Science Bulletin2011,56,16:12
8Controlling factors for gas hydrate occurrence in Shenhu area on the northern slope of the South China Sea显示文摘Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface.WANG HongBin YANG ShengXiong WU NengYou ZHANG GuangXue LIANG JinQiang CHEN DuoFu 2013Science China Earth Sciences2013,56,4:10
9Gas hydrate formation in fine sand显示文摘Gas hydrate formation from two types of dissolved gas (methane and mixed gas) was studied under varying thermodynamic conditions in a novel apparatus containing two different natural media from the South China Sea. The testing media consisted of silica sand particles with diameters of 150-250 μm and 250-380 μm. Hydrate was formed (as in nature) in salt water that occupies the interstitial space of the partially water-saturated silica sand bed. The experiments demonstrate that the rate of hydrate formation is a function of particle diameter, gas source, water salinity, and thermodynamic conditions. The initiation time of hydrate formation was very short and pressure decreased rapidly in the initial stage. The process of mixed gas hydrate formation can be divided into three stages for each type of sediment. Sand particle diameter and water salinity also can influence the formation process of hydrate. The conversion rate of water to hydrate was different under varying thermodynamic conditions, although the formation processes were similar. The conversion rate of methane hydrate in the 250-380 μm sediment was greater than that in the 150-250μm sediment. However, the sediment grain size has no significant influence on the conversion rate of mixed gas hydrate.ZANG XiaoYa LIANG DeQing WU NengYou 2013Science China Earth Sciences2013,56,4:10
10Molecular dynamics simulations of the mechanisms of thermal conduction in methane hydrates显示文摘The thermal conductivity of methane hydrate is an important physical parameter affecting the processes of methane hydrate exploration,mining,gas hydrate storage and transportation as well as other applications.Equilibrium molecular dynamics simulations and the Green-Kubo method have been employed for systems from fully occupied to vacant occupied sI methane hydrate in order to estimate their thermal conductivity.The estimations were carried out at temperatures from 203.15 to 263.15 K and at pressures from 3 to 100 MPa.Potential models selected for water were TIP4P,TIP4P-Ew,TIP4P/2005,TIP4P-FQ and TIP4P/Ice.The effects of varying the ratio of the host and guest molecules and the external thermobaric conditions on the thermal conductivity of methane hydrate were studied.The results indicated that the thermal conductivity of methane hydrate is essentially determined by the cage framework which constitutes the hydrate lattice and the cage framework has only slightly higher thermal conductivity in the presence of the guest molecules.Inclusion of more guest molecules in the cage improves the thermal conductivity of methane hydrate.It is also revealed that the thermal conductivity of the sI hydrate shows a similar variation with temperature.Pressure also has an effect on the thermal conductivity,particularly at higher pressures.As the pressure increases,slightly higher thermal conductivities result.Changes in density have little impact on the thermal conductivity of methane hydrate.WAN LiHua LIANG DeQing WU NengYou GUAN JinAn 2012Science China Chemistry2012,55,1:7
11Characteristics of Upper Mantle Activity in the South China Sea Region and the Indochina Mantle Plume显示文摘According to computed results of the mantle traction field beneath the lithosphere based on satellite-modelled gravity anomalies of different degrees, it has been revealed that the three types of mantle convection on different scales existing in the South China Sea region is the key factor controlling the geodynamics. The mantle convection models on large and middle scales have been proved by natural seismic S-wave tomographic data and interpreted by using the present mantle plume concept In consideration of other relevant geological and geophysical data, the authors put emphasis on discussing the expression form, origin and age of the Indochina mantle plume and its important effect on the conversion of organic matter and hydrocarbon accumulation in Cenozoic basins.WU Nengyou ZENG Weijun LI Zhenwu CHEN Yizhong WEN Xiwen DU Deli LI Guosheng 1999Acta Geologica Sinica(English Edition)1999,73,4:6
12Effect of thermal stimulation on gas production from hydrate deposits in Shenhu area of the South China Sea显示文摘The Shenhu area on the northern continental slope of the South China Sea (SCS) is one of the promising fields for gas hydrate exploitation. The hydrate-bearing layer at drilling site SH2 is overlain and underlain by permeable zones of mobile water. In this study a vertical well was configured with a perforated Interval I for producing gas and a coiled Interval II for heating sediment. The hydrate is dissociated by a small depressurization at Interval I and a thermal stimulation at Interval II. The numerical simulations indicate that the thermal stimulation has a significant effect on gas release from the hydrates in the production duration and improves the gas production in the late period. The gas released by thermal stimulation cannot be produced as quickly as the production gets operated because of the hard pathway for fluids to flow in the sediments. The gas production is enhanced due to the heating for 7242 m 3 in the whole production. Increasing heating temperature at Interval II can improve gas production and restrain water output, and advance the arrival time of the gas flow from the zone at Interval II. The absolute criterion and relative criterion suggest that the thermal stimulation in the production schemes is pronounced for releasing gas from the hydrate deposit, but the production efficiency of gas is limited by the sediment of low permeability. The study provides an insight into the production potential of the hydrate accumulations by thermal stimulation with depressurization in two wells, and a basis for analyzing economic feasibility of gas production from the area.SU Zheng HUANG Li WU NengYou YANG ShengXiong 2013Science China Earth Sciences2013,56,4:4
13Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area,South China Sea显示文摘The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ^(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ^(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ^(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.ZHANG Mei LU Hongfeng GUAN Hongxiang LIU Lihua WU Daidai WU Nengyou 2018Acta Oceanologica Sinica2018,37,7:4
14Simulation of the Accumulation Process of Biogenic Gas Hydrates in the Shenhu Area of Northern South China Sea显示文摘Objective Previous work has largely discussed the relations between sediment structures and accumulation of gas hydrates in the Shenhu area of South China Sea,but has not documented why the gas hydrates occurred at the seafloor topographic highs.Many gas hydrate exploration examples abroad also indicate that the saturation ofLIAO Jing GONG Jianming Lü Wanjun WU Nengyou YUE Baojing LUAN Xiwu HU Gaowei 2016Acta Geologica Sinica(English Edition)2016,90,6:3
15Coupled carbon and sulfur isotope behaviors and other geochemical perspectives into marine methane seepage显示文摘Methane seepage is the signal of the deep hydrocarbon reservoir. The determination of seepage is significant to the exploration of petroleum, gas and gas hydrate. The seepage habits microbial and macrofaunal life which is fueled by the hydrocarbons, the metabolic byproducts facilitate the precipitation of authigenic minerals. The study of methane seepage is also important to understand the oceanographic condition and local ecosystem. The seepage could be active or quiescent at different times. The geophysical surveys and the geochemical determinations reveal the existence of seepage. Among these methods, only geochemical determination could expose message of the dormant seepages. The active seepage demonstrates high porewater methane concentration with rapid SO_4^(2–) depleted, low H_2S and dissolved inorganic carbon(DIC), higher rates of sulfate reduction(SR) and anaerobic oxidation of methane(AOM). The quiescent seepage typically develops authigenic carbonates with specific biomarkers, with extremely depleted ~13C in gas, DIC and carbonates and with enriched ~34S sulfate and depleted ~34S pyrite. The origin of methane, minerals precipitation, the scenario of seepage and the possible method of immigration could be determined by the integration of solutes concentration, mineral composition and isotopic fractionation of carbon, sulfur. Numerical models with the integrated results provide useful insight into the nature and intensity of methane seepage occurring in the sediment and paleooceanographic conditions. Unfortunately, the intensive investigation of a specific area with dormant seep is still limit. Most seepage and modeling studies are site-specific and little attempt has been made to extrapolate the results to larger scales. Further research is thus needed to foster our understanding of the methane seepage.LIU Lihua FU Shaoying ZHANG Mei GUAN Hongxiang WU Nengyou 2017Acta Oceanologica Sinica2017,36,6:2
16Identification of Re-Deposited Sediments and the Relationships with Heterogeneous Distributions of Gas Hydrates in the Shenhu Area显示文摘The first marine gas hydrate drilling expedition(GMGS-1)of China was performed in the Shenhu Area,northern slope of the South China Sea(Fig.1a)by Guangzhou Marine Geological Survey(GMGS)during April to June,2007,to detect the occurrences of gas hydrates.The drilling results showed that the distributions of hydrates in the drilling area were heterogeneous.InSU Ming SHA Zhibin QIAO Shaohua LIANG Jinqiang LIU Jie YANG Rui WU Nengyou 2015Acta Geologica Sinica(English Edition)2015,89,A01:2
17Detection and indication of 1,3,4-C27-29 triol in the sediment of northern South China Sea显示文摘After the detection of the 1,20,21-C_(29) long-chain triol in some sediments and freshwater pteridophytes, in this study, a new homologous long-chain triol, 1,3,4-C_(27-29), is detected for the first time in the Site4 B core sediment in the northern South China Sea. The hydroxyl location and length of the carbon chain of this newly discovered triol differ from those of 1,20,21-C_(29) triol. The test results of its molecular distribution and individual carbon isotope reveal that 1,3,4-C_(29) triol has a good correlation with n-C_(26-30) even carbon-numbered long-chain fatty alcohols, with R^2(n=68) values of 0.905, 0.929 and 0.903, respectively, and its carbon isotope composition, at –32.3‰±1.9‰, is similar to that of n-C_(26-30), at –29.13‰±0.87‰, –32.98‰±1.28‰, and –32.98‰±1.28‰. 1,3,4-C_(29) triol from the Site4 B core sediment and terrigenous long-chain fatty alcohol(n-C_(26-34)) show highly consistent distribution trends in the entire section; thus, the former could serve as a proxy indicator of the terrigenous input. Considering that the 1,20,21-C_(29) triol in previous research belongs to Azolla, which are fresh water pteridophytes, the 1,3,4-C_(27-29) triol identified in this study might have similar biogenetic derivation. Thus, determination of its biogenic area and growing environment could provide potential organic geochemical evidence supporting the terrigenous input and source in the northern South China Sea.ZHU XiaoWei MAO ShengYi WU NengYou JIA GuoDong SUN YongGe GUAN HongXiang WU DaiDai 2016Science China Earth Sciences2016,59,6:2
18High con- centrations of hydrate in disseminated forms found in very fine grained sediments of Shenhu area, South China Sea显示文摘WU Nengyou ZHANG Haiqi SU Xin 2007Terra Nostra2007,,12:1
19Evaluation on gas production potential from laminar hydrate deposits in Shenhu Area of South China Sea through depress- urization using vertical wells显示文摘Su Zheng He Yong Wu Nengyou 2012Journal of Petroleum Science and Engineering2012,86,:1
20Alcohol compounds in Azolla imbricata and potential source implication for marine sediments显示文摘This study investigated the composition of long-chain alkyl diols,triols,sec-alcohols,hydroxyl acids,and other hydroxylated compounds in Azolla imbricata and compared the organic alcohol components of Azolla filiculoides,Azolla microphylla,and South China Sea(SCS)sediments in order to investigate the possible indication of Azolla being the biological source of diols and triols in SCS sediment.Large amounts of diols,monohydroxy acids,and sec-alcohols with internal hydroxy groups atω20 were detected in the three types of Azolla.Among these,1,ω20-diol andω20-hydroxy acid exhibited strong even-odd predominance distribution,whereasω20-sec-alcohol exhibited strong odd-even predominance distribution.In addition,small amounts of diols,triols,and dihydroxy acids with internal hydroxy groups at 9,10 orω9,ω10 were detected,among which the chain length of C_(29)was predominate.Compounds having similar structures as those in Azolla reflected a similar biosynthetic pathway:ω20-hydroxy acid exhibiting even-odd predominance distribution is decarboxylated toω20-sec-alcohol exhibiting odd-even predominance distribution and converted to 1,ω20-diol with even-odd predominance distribution by acyl reduction;ω9,ω10-hydroxy acid is converted to 1,20,21(1,ω9,ω10)-triol by acyl reduction,and then converted to 9,10-diol by hydrogenation and dehydration.The alcohol components in A imbricata were clearly not the biological source of 1,13/1,14/1,15-C_(28,30,32)diols and 1,3,4-C_(27-29)triols in the SCS sediment.Certain marine diatoms might be the source of 1,14-C_(28,30)diol in inshore sediment,but the biological source of diols and triols in the SCS sediment requires further investigation.MAO ShengYi ZHU XiaoWei WU NengYou JIA GuoDong SUN YongGe GUAN HongXiang WU DaiDai 2017Science China Earth Sciences2017,60,2:1
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