Geophysical Signature of the Shallow Water Flow in the Deepwater Basin of the Northern South China Sea     

Xiaohua Zhang  Yunbao Sun  Shiguo Wu 《中国海洋大学学报(英文版)》2018,17(4):791-798

Shallow water flow (SWF), a disastrous geohazard in the continental margin, has threatened deepwater drilling operations. Under overpressure conditions, continual flow delivering unconsolidated sands upward in the shallow layer below the seafloor may cause large and long-lasting uncontrolled flows; these flows may lead to control problems and cause well damage and foundation failure. Eruptions from over-pressured sands may result in seafloor craters, mounds, and cracks. Detailed studies of 2D/3D seismic data from a slope basin of the South China Sea (SCS) indicated the potential presence of SWF. It is commonly characterized by lower elastic impedance, a higher Vp/Vs ratio, and a higher Poisson’s ratio than that for the surrounding sediments. Analysis of geological data indicated the SWF zone originated from a deepwater channel system with gas bearing over-pressured fluid flow and a high sedimentation rate. We proposed a fluid flow model for SWF that clearly identifies its stress and pressure changes. The rupture of previous SWF zones caused the fluid flow that occurred in the Baiyun Sag of the northern SCS.  相似文献   

筑坝拦截对黑河河道沉积物粒度空间分布的影响   总被引：2，自引：1，他引：1  

王昱  连运涛  冯起  王之君  赵维俊  刘娟娟  卢世国  张昕雨 《湖泊科学》2019,31(5):1459-1467

河流沉积物对流域环境变化具有敏感响应，其粒度参数能反映沉积环境中物质来源和水动力环境.本文以黑河流域上中游为研究区域，探究河流沉积物粒度对流域环境变化的响应.从黑河上中游干流22个主要控制断面采集河床沉积物样品，采用筛分法和吸管法对沉积物样品粒度参数进行测定，并分析其空间分布规律对筑坝拦截为主的环境改变响应.研究结果表明：受梯级水库建设影响，黑河上中游泥沙粒径大小差异显著.干流库区泥沙粒径较自然河段明显减小，分选很好，呈正偏或极正偏尖锐分布，而且在库区不同沉积高度上表现出分层沉积特征；坝下游河段因遭受强烈冲刷，较自然河段泥沙粒径粗化显著，分选变差，偏态趋向极正偏，峰态尖锐化；水库回水区受水库壅水及下泄清水的双重制约，泥沙粒度参数介于自然河段和坝下游河段之间，整体分选中等，呈极正偏尖锐分布；沉积环境分析表明，上游支流河段沉积物粒度特征受泥沙供给和物源特征的影响较水动力条件显著，干流河段沉积物粒度特征主要受水动力条件控制.研究结果既符合河流上中游沉积物粒度分布规律，也反映了河流环境变化对沉积物粒度组成的影响.  相似文献   

考虑桩间土体抗滑作用的单排抗滑桩受力计算方法          下载免费PDF全文

肖世国 《中国地质灾害与防治学报》2020,31(1):89-94

为了充分考虑桩间距范围内滑体对抗滑桩受力的影响,从单排抗滑桩加固边坡的整体稳定角度出发,在采用传递系数法分析指定设计安全系数情况下抗滑桩的内力时,提出对一个桩间距范围内的加固坡体进行整体分析,将抗滑桩所在部位单独划分条块,该条块包括桩体受荷段及其两侧桩间距范围内的滑体。推导了与此分析模型相应的桩体受荷段底端内力计算公式,并给出了在滑坡推力线性分布条件下作用于受荷段的净滑坡推力计算表达式。分析结果显示,在不考虑与完全考虑受荷段两侧桩间距范围内滑体抗力作用时,得到是桩体内力及位移的上、下边界值。实例分析进一步表明,理论分析与数值模拟结果具有良好的一致性。所提出的方法比传统方法更有利于抗滑桩设计的经济性。  相似文献   

月球岩石圈弹性厚度研究进展     

钟振  范广学  鄢建国  陈世国 《地质学报》2021,95(9):2692-2702

月球热演化研究需要丰富的月表热流数据.当前唯一的月表热流数据不完全可靠,单一数据也不足代表月球全球热流特征,通过月球岩石圈弹性厚度估算月表热流将会是有效的替代方案.针对弹性厚度估算的问题,概要回顾了以往估算的研究方法和成果,并对近年来利用重力地形导纳估算弹性厚度的理论方法进行了详细的介绍.近年来的研究结果表明月球全球岩石圈的Te可能较小,暗示月表地形形成于岩石圈冷却前较长的一段时间.个别研究成功地估算了个别质量瘤盆地的Te ,但大部分质量瘤盆地的较难估算,这不仅与质量瘤盆地复杂物理过程有关,还可能与岩石圈复杂的补偿机制有关.由于Te仅仅是岩石圈强弱的表征,不同研究方法得出的Te值存在差异是可能的.随着后续探月活动的开展,与国际社会合作布设月球热流载荷,结合后续研究对月球内部结构、月壳和月幔流变学特征的丰富认识,有望优化现有Te估算的理论与方法,进而为全球热流估算及热演化研究提供约束.  相似文献   

Occurrence and exploration of gas hydrate in the marginal seas and continental margin of the Asia and Oceania region   总被引：5，自引：0，他引：5  

Ryo Matsumoto  Byong-Jae Ryu  Sung-Rock Lee  Saulwood Lin  Shiguo Wu  Kalachand Sain  Ingo Pecher  Michael Riedel 《Marine and Petroleum Geology》2011,28(10):1751-1767

Supplies of conventional natural gas and oil are declining fast worldwide, and therefore new, unconventional forms of energy resources are needed to meet the ever-increasing demand. Amongst the many different unconventional natural resources are gas hydrates, a solid, ice-like crystalline compound of methane and water formed under specific low temperature and high pressure conditions. Gas hydrates are believed to exist in large quantities worldwide in oceanic regions of continental margins, as well as associated with permafrost regions in the Arctic. Some studies to estimate the global abundance of gas hydrate suggest that the total volume of natural gas locked up in form of gas hydrates may exceed all known conventional natural gas reserves, although large uncertainties exist in these assessments. Gas hydrates have been intensively studied in the last two decades also due to connections between climate forcing (natural and/or anthropogenic) and the potential large volumes of methane trapped in gas hydrate accumulations. The presence of gas hydrate within unconsolidated sediments of the upper few hundred meters below seafloor may also pose a geo-hazard to conventional oil and gas production. Additionally, climate variability and associated changes in pressure-temperature regimes and thus shifts in the gas hydrate stability zone may cause the occurrence of submarine slope failures.Several large-scale national gas hydrate programs exist especially in countries such as Japan, Korea, Taiwan, China, India, and New Zealand, where large demands of energy cannot be met by domestic supplies from natural resources. The past five years have seen several dedicated deep drilling expeditions and other scientific studies conducted throughout Asia and Oceania to understand gas hydrates off India, China, and Korea. This thematic set of publications is dedicated to summarize the most recent findings and results of geo-scientific studies of gas hydrates in the marginal seas and continental margin of the Asia, and Oceania region.  相似文献   

Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, South China Sea   总被引：4，自引：0，他引：4  

Xiujuan Wang  Shiguo Wu  Myung LeeYiqun Guo  Shengxiong YangJinqiang Liang 《Marine and Petroleum Geology》2011,28(9):1625-1633

During the China’s first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ∼10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity.  相似文献   

南海南部大陆架的残留沉积   总被引：1，自引：0，他引：1  

吴时国  罗又郎 《热带海洋学报》1994,(3)

研究了南海南部大陆架的残留沉积物的粒度、石英砂表面结构特征、生物分布等，并指出残留沉积普遍遭受改造。按其早期的形成环境差异和改造作用不同，划分出加里曼丹－巴拉望残留沉积区和亚南巴斯－纳土纳残留沉积区。  相似文献   

海洋古生产力重建初探──以南沙群岛海区NS90-103柱样为例     

吴时国  涂霞  罗又郎 《海洋科学》1996,20(2):47-51

以南沙海区ＮＳ９０－１０３柱样为例，利用各种古生产力指标物，如有机碳含量，有孔虫壳和有孔虫碳同位素，重建了２０００００ａ以来古生产力变化，并对结果予以讨论。  相似文献   

深水钻井中浅水流灾害问题及其地球物理识别技术   总被引：6，自引：0，他引：6  

董冬冬  赵汗青  吴时国  伍向阳 《海洋通报》2007,26(1):114-120

在深水钻井中,浅水流是一种常见的地质灾害。中国正在进行深水油气勘探,十分有必要开展这方面的地质灾害研究。介绍了浅水流的形成机制及地球物理特性。目前用于识别和预测浅水流的手段有测井和反射地震两大类方法。主要介绍了几种用于参数提取的地震反演方法,如传统Dix反演、叠后振幅反演、层析反演、叠前振幅反演等。  相似文献   

Identification of Fucans from Four Species of Sea Cucumber by High Temperature ~1H NMR     

WU Nian  ;CHEN Shiguo  ;YE Xingqian  ;LI Guoyun  ;YIN Li' ang  ;XUE Changhu 《青岛海洋大学学报(英文版)》2014,(5):871-876

Acidic polysaccharide, which has various biological activities, is one of the most important components of sea cucumber. In the present study, crude polysaccharide was extracted from four species of sea cucumber from three different geographical zones, Pearsonothuria graeffei（Pg） from Indo-Pacific, Holothuria vagabunda（Hv） from Norwegian Coast, Stichopus tremulu（St） from Western Indian Ocean, and Isostichopus badionotu（Ib） from Western Atlantic. The polysaccharide extract was separated and purified with a cellulose DEAE anion-exchange column to obtain corresponding sea cucumber fucans（SC-Fucs）. The chemical property of these SC-Fucs, including molecular weight, monosaccharide composition and sulfate content, was determined. Their structure was compared simply with fourier infrared spectrum analyzer and identified with high temperature 1H nuclear magnetic resonance spectrum analyzer（NMR） and room temperature 13 C NMR. The results indicated that Fuc-Pg obtained from the torrid zone mainly contained 2,4-O-disulfated and non-sulfated fucose residue, whereas Fuc-Ib from the temperate zone contained non-, 2-O- and 2,4-O-disulfated fucose residue; Fuc-St from the frigid zone and Fuc-Hv from the torrid zone contained mainly non-sulfated fucose residue. The proton of SC-Fucs was better resolved via high temperature 1H NMR than via room temperature 1H NMR. The fingerprint of sea cucumber in different sea regions was established based on the index of anomer hydrogen signal in SC-Fucs. Further work will help to understand whether there exists a close relationship between the geographical area of sea cucumber and the sulfation pattern of SC-Fucs.  相似文献