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1.
琼东南盆地深水区生物礁生长环境及分布特征分析   总被引:1,自引:0,他引:1  
生物礁储层是一种典型的油气储层,具有非常大的油气勘探潜力.位于南海北部大陆边缘的琼东南盆地,在形成演化过程中出现了有利于生物礁发育的环境.盆地南部深水区远离物源,在构造演化过程中产生了较多的构造隆起,在这些构造隆起的周缘适合生物礁的发育.通过地震资料解释认为,琼东南盆地南部深水区发育有规模大小不等的生物礁,而且这些生物礁的发育与构造演化的阶段可以对应起来,应具有较好的油气勘探潜力.  相似文献   

2.
目前琼东南盆地北礁凹陷中中新统梅山组顶部丘形反射引起广泛关注,但对其成因有不同认识。本文通过高精度二维、三维地震、钻井资料,研究丘形反射的特征。研究表明北礁地区梅山组顶部发育近东西向展布的长条形丘体,丘间为水道,丘内为中-弱振幅的地震反射,与西南部强振幅水道砂岩形成鲜明的对比,波阻抗反演揭示丘内为低波阻抗,属泥岩范畴。梅山组塑性丘内地层发生重力扩展,在其上覆的脆性地层(强振幅砂岩和弱振幅泥岩)发育多边形断层,反推出梅山组形成于深水环境,丘为泥丘,沉积环境分析也认为北礁凹陷中中新世为半深海沉积,梅山组的丘-谷分别对应上覆地层的谷-丘,认为是底流剥蚀/沉积成因。本文的研究对南海北部丘形反射的认识有重要意义,并可降低油气探勘风险。  相似文献   

3.
南海琼东南盆地北礁凹陷中中新统梅山组顶部丘形反射目前引起广泛关注,前人推测为生物礁、重力蠕动与底流叠加成因、等深积丘等。本文通过钻井资料、二维、三维地震资料精细刻画丘形反射(残丘)和丘间水道特征及其成因。残丘及水道在北礁凸起不发育,在边缘斜坡中部和高地较发育,且有向高地两边规模减小趋势,不具对称性,残丘和水道呈平行-亚平行近E-W向展布,局部有合并分叉现象,与北礁凸起走向呈一小角度;丘宽562~1 223 m,丘高29~87 m,丘长10 km左右,存在丘翼削蚀,水道底蚀现象。地震属性分析表明三维工区西南部残丘间水道由砂泥岩互层充填,形成长条形强振幅,而残丘为中-低振幅;地震、钻井资料分析表明丘形反射(残丘)由钙质泥岩和泥岩组成,属于半深海沉积,且残丘内部波阻抗为5.0×106~6.5×106kg/m3·m/s,低于火山岩、灰岩波阻抗,属于砂泥岩地层范畴;根据梅山组下段水道由西向东强振幅变弱、分叉、前积反射和海山附近底流(等深流)沉积剥蚀特征综合判定底流古流向自西向东,根据海山两翼地震反射特征推测底流可追溯至晚中新世早期(11.6 Ma BP),综合分析认为,研究区中中新统梅山组丘形反射是晚中新世早期底流切割梅山组地层形成的残丘。  相似文献   

4.
西沙海槽盆地处于南海北部陆坡洋陆壳过渡带,为一个分割南海北部陆架和西沙地块的新生代裂谷盆地,其沉积环境演化研究有助于进一步认识南海形成演化过程。通过南海陆坡区域地震地层对比,将西沙海槽盆地新生代以来划分出9个地层单元,采用地震线描和地震相分析方法,恢复各地层单元沉积时期的地层结构及古地貌,探讨其沉积环境演化过程。结果表明,古新世—始新世西沙海槽盆地为河流和湖泊沉积环境;渐新世—早中新世初,演变为分割南海北部陆架和西沙地块古陆、贯通琼东南盆地和西北次盆的海峡,沉积环境由滨-浅海过渡到半深海环境;中中新世以来盆地进入陆坡海槽发育阶段,晚中新世以后中央水道形成,演变为一个陆坡内深水海槽,为海流和浊流通道,整体处于半深海-深海沉积环境。  相似文献   

5.
新近纪以来,在南海海域陆架边缘、陆坡隆起和深海火山岩隆等构造背景上,发育了大量的生物礁滩沉积体。受沉积环境和基底的控制,不同地区的生物礁发育时间与沉积特征有所不同。中建礁位于西沙群岛西侧,与西沙群岛区生物礁不同,是在南海北部陆坡隆起背景上发育形成的孤立生物礁。在前人现代生物礁调查的基础上,首次对中建礁开展了船载重磁、二维地震和三维地震勘查,并采用地震层序地层和地震沉积学解释方法,对中建礁重力、磁力和地震资料进行了系统分析,在中建礁区识别出5个地震层序界面,明确了中建礁基底的岩性特征及形成时间;并通过对礁前斜坡扇的研究,认为中建礁经历了中中新世、晚中新世和上新世以来等3个发育阶段。  相似文献   

6.
生物礁为南海周边区域重要的油气储层类型,本次基于XK-1井岩心及薄片中主要造礁生物种类、数量、分布规律与生态特征的分析,开展了西沙地区中新世以来碳酸盐岩-生物礁演化过程的研究,并推测了盆地内生物礁的发育特征。研究认为西沙地区中新世以来主要发育珊瑚、钙藻及苔藓虫三类造礁生物,同时,根据其分布特征,结合建立的礁、滩复合体沉积模式将XK-1井中新世以来的沉积环境划分为13个演化阶段。提出伴随着海平面的上升,造礁生物有从珊瑚逐渐向钙藻及苔藓虫演变的趋势,而伴随着海平面的下降,造礁生物又从钙藻和苔藓虫逐渐向珊瑚演变。明确了该区中新世以来发育早中新世三亚组一段沉积时期、晚中新统黄流组沉积时期、上新统莺歌海组沉积晚期至第四纪乐东组沉积时期3个主要造礁期和早中新世三亚组二段沉积早期、中中新世梅山组沉积中期2个次要造礁期。  相似文献   

7.
南海北部深水区盆地特征及其动力学背景   总被引:4,自引:0,他引:4  
袁玉松  丁玫瑰 《海洋科学》2008,32(12):102-110
南海北部陆缘深水区指水深〉300m的陆缘盆地区,包括琼东南盆地中央坳陷带及其南部隆起区、神狐隆起南侧、珠江口盆地珠二坳陷及其南部的西沙-中沙隆起和一统暗沙隆起区(图1),总面积超过120000km^2。2006年,从南海北部陆缘珠江口盆地白云凹陷水深1480m的荔湾构造上钻探的LW3—1—1井获得天然气重大发现,  相似文献   

8.
新近系生物礁油气储层是南海含油气盆地油气勘探两大主力目的层系之一,过去有关其高精度层序地层学和层序演化模式的研究不多.为此,通过对北康盆地2万余公里地震资料的精细解释和钻井资料的综合研究,获得了以下重要成果:1)识别划分出该盆地新近纪11条主要等时界面、7个三级层序和基本层序组.2)描述了生物礁低位体系域、海侵体系域和高位体系域地震反射结构特征.3)提出南海首个中中新世生物礁高精度层序演化模式,代表中中新世(16.3-10.4Ma BP)海宁期(T13-T2)生物礁的剖面形态,含由1个低位体系域层序单元+5个高位体系域层序单元构成的一个典型海进体系域和由1个早期高位体系域层序单元+1个晚期高位体系域层序单元构成的1个典型高位体系域;可见中中新世完整海进-海退旋回生物礁发生、发展和消亡的过程.通过与曾母盆地中新世生物礁解释剖面对比,指出该模式具有区域性古海洋学代表意义.4)通过对L礁、西琛一井和南海-地中海中新世古海洋演化研究,确定研究区中中新世分别发育5-8个海平面升降旋回,形成晚中新世"南中国海事件",具有冰川型海退性质,可与全球和南海北部特别是与"Missinian"事件对比;确定北康盆地乃至南海新近系生物礁形成至逐渐消亡,也是新构造运动与新近纪古海洋事件共同作用的结果.5)指出L礁气田发现有9.8Ma BP、13.8Ma BP、14.5Ma BP和15.5Ma BP等多个层序界面,分别系高孔渗层段;同期南海礁型油气圈闭层序界面当为优良储层;若其为油气充满,则油气"高产"或构成"高压气包".以上成果,将有助于对全球变化及南海古海洋区域响应过程与结果的理解,并对南海的油气勘探有启示作用.  相似文献   

9.
南海北部深水区东西构造差异性及其动力学机制   总被引:1,自引:0,他引:1  
南海北部深水区位于南海洋陆转换带,构造运动活跃,构造特征复杂。同时,南海北部深水区石油、天然气、天然气水合物等矿产资源丰富。因此,加强南海北部深水盆地构造特征分析,揭示南海北部陆缘构造属性与南海形成演化机制,对于南海深部过程演变研究、油气资源评价与地质灾害防治等具有重要的意义。本论文通过对南海北部深水区陆架-陆坡结构、盆地构造特征与演化规律的分析,指出研究区东西存在明显的构造差异性,并分析了其动力学机制。南海北部深水区东部陆架-陆坡结构为宽洼窄隆型,而西部为窄洼宽隆型。东部珠江口盆地深水凹陷均为半地堑结构,剖面上呈不对称的箕状;西部琼东南盆地除北礁凹陷为南段北超的小型半地堑外,其它凹陷均为地堑结构,为南北双断式沉积体系。在构造演化方面,东部中中新世末结束裂后期进入新构造活动期,白云凹陷构造活动性增强,表现为快速的沉降和显著的晚期断裂作用;而西部晚中新世末才进入新构造活动期,深水区表现为快速沉积作用,断裂活动较弱。  相似文献   

10.
梅山组海底扇作为中央峡谷水道之外最引人注目的大型储集体,是琼东南盆地尤其是深水区常规碎屑岩领域下一步最为重要的勘探对象。总结了琼东南盆地各凹陷钻井资料所揭示的梅山组海底扇差异分布现象,通过研究区大陆架发育特征、陆架坡折带发育特征,结合物源供给与优势海流方向,首次从宏观格局解释了琼东南盆地中央坳陷带不同凹陷海底扇发育地质背景的差异及成因,提出乐东凹陷梅山组大型海底扇主物源来自东北方向海南隆起。通过细化中中新世大海退内部次级海平面旋回特征,首次建立了本区梅山组层序充填与海平面旋回的精确对应关系,从层序成因角度厘清了梅山组各期次海底扇发育演化特征与凹陷级别的有利储层展布特征,并据此提出相应的勘探建议,指出乐东凹陷梅山组中-晚期海底扇储层风险低,是梅山组海底扇领域突破的首选区带;陵水凹陷早期海底扇圈闭有效性较好,是梅山组海底扇大规模成藏的有利勘探方向。该研究为梅山组海底扇领域的勘探部署提供了新思路。  相似文献   

11.
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   

12.
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   

13.
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.  相似文献   

14.
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   

15.
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   

16.
Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.  相似文献   

17.
This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.  相似文献   

18.
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.  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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