Respondence Between Carbon and Oxygen Isotopic Characteristics of Foraminifera from the Northern South China Sea and Late Quaternary Hydrate Released

为探寻晚第四纪以来水合物分解事件在南海北部甲烷渗漏环境下有孔虫中的记录,对南海北部陆坡2个区块的沉积柱状样有孔虫碳氧同位素组成和测年分析发现,底栖有孔虫uVIgErInA SPP.碳同位素值为-2.12‰~-0.21‰,浮游有孔虫glObIgErInOIdES rubEr.氧同位素值为-3.11‰~-0.60‰,zd3、zS5 2个柱状样孔底年龄分别为26 616、64 090 A,对应了氧同位素Ⅲ、Ⅳ期末期,有孔虫碳同位素负偏的层位与氧同位素Ⅱ、Ⅳ期(冷期)层位相对应,负偏程度达到了-2‰,与布莱克海台和墨西哥湾等地区晚第四纪沉积层中有孔虫碳氧同位素组成相似。分析认为:研究区是典型的甲烷渗漏环境,该区在氧同位素Ⅱ、Ⅳ期,由于全球海平面下降,导致海底压力减小,天然气水合物分解释放,具轻碳同位素的大量甲烷释放进入海底溶解无机碳(dIC)池并记录在有孔虫壳体内,造成有孔虫碳同位素负偏;同时在有孔虫负偏层位黄铁矿和自生碳酸盐较发育,进一步证实了有孔虫碳同位素受甲烷影响较大,而海洋生产力的降低和早期成岩作用对有孔虫碳同位素负偏的影响较小。To search the records of the gas hydrate decomposition events under methane seepage condition since the late Quaternary,carbon and oxygen isotopes analysis and radiometric dating of foraminifera from sediment cores collected from three different blocks of the northern slope of the South China Sea are carried out.The results show:1) the carbon isotope value of benthic foraminifera Uvigerina spp.is-2.12 ‰ to-0.21 ‰ and oxygen isotope value of planktonic foraminifera Globigerinoides ruber is-3.11 ‰ to-0.60 ‰;2) the age of the two cores at the bottom of ZD3 and ZS5 drills are 26 616 a and 64 090 a respectively,corresponding to the early oxygen isotope stage Ⅲ and the end of Ⅳ;3) negative-skewed layer of carbon isotope(up to-2 ‰) corresponds to that of oxygen isotope stage Ⅱ(cold period);4) the foraminifera oxygen isotopic compositions are similar to those from the Late Quaternary sediments of Blake Ridge and the Gulf of Mexico.According to our analysis,the reasons include :1) the study area is under a typical methane seep environment in the area at oxygen isotope stageⅡ;2) due to global sea-level fall,water pressure at the sea floor decreases,gas hydrate decomposed and released;3) large amount of light carbon isotopes of methane were released into the sea inorganic carbon(DIC) pool and were recorded in the foraminifera shell.Pyrite layers developed in the negative bias layers of foraminifera further supports our views that the carbon isotope of the foraminifera were affected by methane more intensely than by the reduction of marine productivity and by early diagenesis.国家“973”计划项目(2009CB219501);国家自然科学基金项目(40976035

Magnitude of dissociation of methane hydrate reservoir associate with climate change

Methane hydrates are found in enormous quantities along all the continental margins. The magnitude of the carbon pool locked in the methane hydrate reservoir is not known precisely, but estimates range from 10(3) to 10(6) Gt C. Methane hydrates are also of interest because of their potential role in climate change. When these marine methane hydrates begin to dissociate, the methane trapped in the methane hydrates is released into the ocean and the atmosphere. This review focuses on the dissociation mechanism of methane hydrates that are rather unique and involve a number of conditions, and presents current understanding of the effects of methane hydrate on the chemical and physical properties of seawater. We discuss past events about the dissociation of methane hydrate in the various geological periods. It will be shown how the previously mentioned sufficient flux of methane from hydrate dissociation can cause an oceanic anoxic event and a major global warming. These events maybe are occurring and will be believed to influence the climate change in the future

Geochemical characteristics of pore water in shallow sediments from north continental slope of South China Sea and their significance for natural gas hydrate occurrence

Northern slope of the South China Sea is a potential area of gas hydrates and research focus areas. Analyzed geochemical parameters about pore water of the anions and cations of major components and delta C-13(DIC) in the sediments from Shenhu sea area, Dongsha sea area and Southwest Taiwan Basin and collected by gravity piston. The results showed that Cl- concentration were no significant changes with depth at the three stations and their values were consistent with the normal sea water, SO42- concentration showed significant changes in gradient descent from core top to bottom at three stations and Ca2+, Mg2+, Ca2+/Mg2+ showed a similar downward trend with SO42- concentration, but the amplitude is inconsistent. The SMI of Shenhu sea area, Dongsha sea area, Southwest Taiwan Basin were separately 11m, 8m, 6m and delta C-13(DIC) of pore water in the sediments range from -10 parts per thousand to -27 parts per thousand, which were similar with geochemistry characteristics of pore water in the sediments at other international regions of being found gas hydrate, such as Blake Ridge and Mexico Gulf. These geochemistry characteristics may suggest that natural gas hydrate reservoir released methane in deep sediments and methane was mixture gas as main causes of pyrolysis. Summary a series anomaly indicators and identification methods that use these geochemical anomalies characteristics about pore water of shallow sediments to trace gas hydrate in deep stratum. (C) 2011 Published by Elsevier B. V. Selection and/or peer-review under responsibility of National University of Singapore

New screening method for reservoir by CO_2 injection miscible flooding

注CO2混相驱是一种提高原油采收率的重要手段,实施该方法的关键是筛选出具有开发潜力的油藏。目前,在注CO2混相驱油藏的筛选上,缺乏统一的筛选指标和筛选方法。通过对国内外注CO2混相驱油藏开采情况的分析和对比研究,选取了影响注CO2开采效果的12个筛选指标,利用概率与数理统计方法提出了筛选指标的评价标准,并应用模糊优选理论和模糊层次分析法,建立了区间数注CO2混相驱油藏筛选模型。应用该筛选方法对6个典型的候选油藏进行了筛选排序和综合评价。结果表明,该方法能够客观地评估油藏注CO2开发潜力的大小。CO2 injection miscible flooding is an important method for enhanced oil recovery(EOR).It is important to screen out the potential reservoirs for using the method.Now,there aren t uniform screening indexes and method about screening out CO2 injection miscible flooding reservoirs.Based on the analysis and researches of the CO2 injection miscible flooding reservoirs,12 indexes affecting CO2 injection miscible flooding results were picked out.By the method of probability statistics,the assessment criterions were brought forward.And combining with fuzzy optimum and fuzzy analytical hierarchy process(FAHP),the interval number screening model for CO2 injection miscible flooding reservoirs was successfully established.This screening method was used to screen and assess six classical candidate reservoirs about CO2 injection miscible flooding.The results show that the method could perfectly evaluate and screen the potential of CO2 injection of the candidate reservoir.国家自然科学基金项目(40472156

Equilibrium PT curve of methane hydrates in the presence of AlCl3

Using an experimental transparent sapphire high-pressure cell, three-phase (methane hydrate + AlCl3 solution + methane) equilibrium conditions of methane hydrates in the aqueous solution containing AlCl3 have been investigated under conditions of temperature from 272.15 to 278.15 K and pressure from 4.040 to 8.382 MPa. It could be clearly verified that AlCl3 is of stronger inhibitive effect than that observed for other electrolytes, such as KCl, CaCl2, at the same mole fraction. The induction time of the methane hydrate formation becomes longer when the water activity decreases with the increase of ion charge numbers. Methane hydrates tend to crystallize more easily with higher concentration (AlCl3 concentration of 18%) than lower one (AlCl3 concentration of 10%) in the same electriclyte solution. An empirical exponential equation is presented to calculate the equilibrium temperature and pressure of methane hydrate stable occurrence, and to correlate the measured data for aqueous AlCl3 solution. The results shove that there was infinitely small discrepancy between the theoretical computed values and the data oberserved in actual experiments

Coupled Relationship among Hydrate Structure,Hydration Number, and Raman Spectrum

为了探讨不同气体组分和环境介质对形成笼状结构类型水合物和水合数的影响, 开展了一元体系 (CH4、CO2、C3H8 )和二元体系(CH4 +CO2、CH4 +C3H8、CH4 +N2 )的水合物生成结晶充填过程、结晶构型和动力学特性分析, 并对生成的水合物进行了拉曼光谱分析。结果表明单组分甲烷充填小孔穴 512和大孔穴 512 62 形成Ⅰ型笼状结构水合物(SⅠ), 二氧化碳和丙烷只占据大孔穴 512 64 形成Ⅱ型笼状结构水合物 (SⅡ ); 而二元混合组分中小孔穴中只充填有甲烷, 而没有CO2、N2 和C3H8。应用反褶积的ν1 对称谱带测定了CH4 分子在Ⅰ型结构大孔穴和小孔穴中的相对占有率,并根据谱带的面积比(对应于小孔穴与大孔穴)计算了平衡条件下甲烷水合物孔穴占有率及其耦合的水合数, 认为气体分子的大小不仅影响它所充填的孔穴形态和类型, 而且影响水合物生成的结构类型和水合数。To discuss the affects of the different gas compositions and environment media on the forming of the different complicated clathrate hydrates with the different structure types,and hydration numbers, this study (analyzed) the crystal filling process of the hydrate, the crystal construction type,and the dynamics characteristics in the singleness system(CH_4, CO_2, and C_3H_8,respectively)and in the duality system(CH_4+CO_2, CH_4+C_3H_8, and CH_4+N_2,respectively), and proceeded to analyse the results using Raman spectra. The results show that the methane fills the small cavities of 5~(12) and the large cavities of 5~(12)6~2 forming structure Ⅰ clathrate hydrate((SⅠ)),CO_2 and C_3H_8 only occupy the large cavities of 5~(12)6~4 forming structure Ⅱ clathrate hydrate((SⅡ) )in the singleness system,and that in the duality system the small cavities are only filled by CH_4,neither CO_2 nor N_2 and C_3H_8 is found. Applying the deconvoluting v_1 symmetric bands to measure the relative (occupancy) factors of CH_4 in the large cavities and in the small cavities of SⅠ, and according to the area ratio (corresponding to the small cavities and to the large cavities) of the bands, and computing the cavity occupancy factors and the coupling hydration numbers of methane hydrate under a few equilibrium terms,it is shown that the size of the gas molecule not only affects the appearance and the type of the filling cavities , but also do the structure type and the hydration number of hydrates.国家自然科学基金项目(40272066; 40472156);; 教育部厦门大学“211”工程资助项目

土荆芥生长土壤的环境地球化学特征

目的研究土荆芥生长土壤地球化学特征,为土荆芥gAP管理提供环境因素的依据。方法通过对地道药材土荆芥生长环境的实地调查,并采集其生境土壤样品进行元素分析及研究适宜的肥力条件。结果土荆芥适宜生长土壤为中性或弱碱性沙质土壤,其生长土壤肥力较高,而且分析发现其中A l2O3,k2O,n I,zn,rb,bA的含量明显高于福建省及全国土壤中的平均值,含有丰富的微量元素,nA2O,k2O含量高于非生境土壤,而A l2O3,fE2O3,CAO,TIO2低于非生境土壤,且土荆芥对P、CA有选择性的富集作用。结论土壤的地球化学特征对土荆芥的生长有影响

An Overview of the Concept of Regional Sediment Management

就"区域沉积物管理"(简称RSM) 概念与方法进行了系统论述,以厦门地区为例阐述了 RSM 研究的必要性和重要性,并对如何应用区域沉积管理来处理海岸冲刷、淤积与港口码头建设过程中可能遇到的问题进行了深入浅出的讨论,同时,提出了发展 RSM 的战略构想与框架。In this article we described the concept of "regional sediment management" (RSM), and identified opportunities for and impediments to implementing regional approaches to sediment management, and also summarized the background information and applications of RSM. Furthermore, we considered the needs of RSM studies and, suggested the framework for developing RSM strategies, and described the specific studies for the Xiamen region

沉积物粒度参数的无偏估计及其在长乐海岸的应用

根据数理统计方法对粒度参数进行无偏估计,使之较以往参数估计更符合无系统误差的这一估计量的评选标准,并用这一方法对长乐东部海岸的风沙进行了系统的粒度参数分析,结果表明长乐海岸风沙沉积物的主要粒级为细沙,分选好,偏度为近对称,峰态很窄等特征,说明研究区域海岸风沙的搬运风动力主要为NE向、而且动力强度较稳定。福建省自然科学基金“福建海岸风沙形成机理及危害的防治研究”(D0410009

Dynamic simulation of gas hydrate reservoirs in the Shenhu area,the northern South China Sea

为进一步了解南海北部神狐海域天然气水合物的成藏匹配条件,利用典型二维地震剖面,构建了该区的地质模型,并对其进行了天然气水合物成藏动力学的模拟。研究结果表明:神狐海域具备天然气水合物成藏的温度、压力条件;生物气和热解气的资源潜力巨大,满足水合物形成的气源条件;运移条件优越,有利于天然气水合物的聚集成藏。并提出了该区天然气水合物的成藏模式。The north slope of the South China Sea is structurally characterized by a passive continental margin and has various Cenozoic oil-and gas-bearing depositional basins,where hydrocarbon resources are abundant,and the geological and tectonic settings,the temperature and pressure regimes as well as the methane-generative potential of thick organic-rich sediments are all favorable for the formation of gas hydrate.As a result,this region is also an ideal area for studying gas hydrate accumulations.In order to understand natural conditions of the gas hydrate formation,based on the typical 2-dimensional seismic image of the Shenhu area,a geological model of gas hydrate reservoirs was established and a dynamic simulation of gas hydrate accumulations was carried out as well.The results indicated that the temperature and pressure of the Shenhu area are appropriate for gas hydrate accumulations,source rocks there have a huge gas-generative potential and hydrocarbon migration conditions are favorable,providing an abundant gas source and good pathways for the gas hydrate formation.A forecasting model of the gas hydrate formation was given based on basin analysis,indicating that the Shenhu area is a better prospect area of gas hydrate because of its huge potential of gas hydrate resources.国土资源部公益性行业科研专项(200811014)“天然气水合物成藏的控制因素研究”;国家自然科学基金项目(No.40930845)“南海北部深水盆地油气渗漏系统与天然气水合物富集机制研究”;国家重点基础研究发展规划(973)项目(2009CB219501)“南海北部天然气水合物成藏的气源条件研究”联合资