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ChristineEcker 《海洋地质》2002,(1):10-20
南卡罗莱纳布莱克海台的海洋地震数据和测井表明明显的似每底反射（BSR）是由含天然气水合物的沉积层覆盖在含游离气的沉积上所形成。我们将一个理论的岩石物理模型应用到二维的布莱克海台海洋地震数据上以确定天然气水合物及游离气的饱和状态。高孔隙度海洋沉积作为一个粒状的系统建立模型，在这样的系统中弹性波速度与孔隙度、有效压力、矿物、孔隙充填物的弹性性质地、水、以及孔隙中天然气水合物的饱和度联系在一起。为了将这种模型应用到地震数据上，首先我们使用迭加速度分析得到层，然后通过地质信息估算出孔隙度和饱和度，我们首先假设沉积物中没含天然气水合物或游离气，然后使用岩石物理模型直接从层速度计算孔隙度。这种孔隙度剖面在有天然气水合物及游离气的地方表现出异常（与所期望的典型剖面以及在无天然气水合物或游离气存在的沉积中得出的剖面相比较）。在含天然气水合物的地方孔隙度估算不足而在含游离气存在的沉积度估算过高。从这些异常剖面中，通过与典型孔隙度剖面（不含天然气水合物及游离气）相减计算出孔隙度的剩余值。然后，通过引入天然气水合物或游离气的饱和度，应用岩石物理模型消去这些异常。这样一来就得出了所期望的二维饱和度分布图。我们得出最大的天然气水合饱和度介于孔隙空间的13%到18%（取决于所用模型版本的不同而有所变化）。这些饱和度数值与布莱克海台的测井结果（在地震测线边上）相吻合，测井的结果为12%。游离气的饱和度在1%和2%之间。饱和度的估算对输入的速度值极为敏感，因此精确的速度确定对储量的改正十分关键。 相似文献
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南海陆坡天然气水合物饱和度估计 总被引：5，自引：0，他引：5
基于双相介质理论和热弹性理论,建立了沉积层纵波速度与天然气水合物饱和度、弹性性质及地层孔隙度之间的关系。通过对比饱和水的理论P波速度与实际P波速度,可以得到天然气水合物饱和度。根据ODP184航次的电阻率、声波速度、密度等测井资料以及地质资料,初步推断南海陆坡存在天然气水合物。根据声波测井的纵波速度估算出南海1146和1148井天然气水合物饱和度分别为孔隙空间的25％～30％和10％～20％,1148井个别沉积层天然气水合物饱和度可达40％～50％。沉积层的纵波速度与饱和水速度差值越大,天然气水合物饱和度越高。 相似文献
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采用岩石物理合成地震模型，我们解释了弗罗里达近海BSR振幅随炮检距变化，现场地震资料的AVO分析和以往得出的速度结果对比显示：BSR将含游离甲烷的沉积物与含水合物沉积物分隔开来，BSR振幅随偏移跨增大呈负增长，这种特性说明BSR之上的P波速度比BSR之下的P波速度要大，BSR之上的S波速比BSR之下的波速度小。由此可见，用AVO和速度结果可帮助推断水合物沉积物内部结构。为了达到这个目的，建立两种微力学模型，对应于孔隙空间内水合物沉积的两种特殊情况：（1）水合物胶结颗粒接触，并增强了沉积物强度；（2）水合物远离颗粒接触部位，并未影响沉积积物骨架的硬度。仅第二种模型能定量化形成所观察到AVO响应。因此，推断含水合物沉积物内部结构意味着：（1）BSR之上的沉积物未胶结，故机械强度关弱；（2）其渗透率低，因为水合物阻塞了孔隙空间孔道。后者解释了为什么游离气圈闭在BSR之下，地震资料也暗示水合物层顶部缺少强反射，这一事实建议恰恰在BSR之上的沉积物内水合物浓度高，随深度减少逐渐降低，这种影响与BSR之上的低渗透水合物沉积物阻止游离甲烷上运移一致。 相似文献
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在世界各地陆架外缘的地震剖面上，出现与海底近似平行的拟海底反射层BSR。BSR与气体水合物稳定域同时发生，并通常用作指示海底天然气水合物。尽管假设BSR标志含气体水合物的沉积物之底界，但位于BSR之下沉积物内低速游离气的产状及重要性仍是长期争论的课题。这篇论文通过对俄勒冈近海和波弗特海面两个地区BSR的反射系数模拟或AVO模拟，调查水合物丰度与BSR伴生的游离气。根据两地的多道地震剖面，地震速度资料和俄勒冈ODP第892站的钻井记录资料模拟，若BSR之上的气体水合物饱和度小于孔隙体积的30％，BSR的AVO研究能确定BSR之下是否存在游离气。根据AVO，能大致估算BSR之上气体水合物饱和度，但仅用地震资料，不能控制BSR之下的游离气饱和度。两个地区的AVO分析暗示出：BSR之下的游离气是导致强振幅BSR的主要原因。对两地区研究，计算BSR之上的水合物浓度不足孔隙体积的10％。 相似文献
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为了更好地研究天然气水合物展布形态和赋存情况,利用AVO反演技术对琼东南海域天然气水合物进行了识别。首先通过对不同地层模型下天然气水合物和游离气的AVO属性特征进行了正演模拟分析,获得了天然气水合物AVO属性的响应特征。研究表明,天然气水合物饱和度不同时,其BSR处AVO属性特征也不同。当天然气水合物饱和度较高时,BSR处的AVO属性特征为:截距为负值,梯度为正值,截距×梯度为负值,流体因子为负值;当饱和度较低时,受游离气的影响,其BSR的AVO属性特征为:截距为负值,梯度为负值,截距×梯度为正值,流体因子为负值且幅值较大。鉴此,根据正演分析结果,重点对琼东南海域地震资料进行了天然气水合物AVO属性异常分析,判识确定该区具有高饱和度水合物的AVO属性特征,其天然气水合物勘探潜力大。 相似文献
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南极南设得兰群岛岸外BSR地震层析研究 总被引：1，自引：0，他引：1
为了重构没积层序中与气体水合物和游离气层相联系的速度场，地震反射层析已经在南设得兰群岛边缘的增生锲两个多道地震剖面中得到应用。地震资料显示沿着水深1000－4600m的斜坡范围内存在强BSR，在局部地区比一个弱的正极性反射深80ms。分析表明从海底到BSR处速度趋势与海洋沉积在正常条件下的趋势一致，而在BSR和下伏反射层之间速度突然降低，这说明在孔隙空间中存在游离气。计算获得游离气层厚度大约为50ms。局部地层BSR上方速度的增大，就象叠前深度偏移剖面一样，一是由于正常压实沉积层中水合物含量较丰富；二是由于沉积过压实。我们发现南设得兰群岛大陆斜坡水合物和游离气的分布受到增生锲的构造背景控制，断层起到了促使天然气向表层运移的通道作用。文中将简要地描述所采用的层析方法。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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《海洋学报(英文版)》2014,(8):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
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Nabil Sultan Pierre Cochonat Jean Fran ois Bourillet Florence Cayocca 《Marine Georesources & Geotechnology》2001,19(2):107-133
This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed. 相似文献