排序方式： 共有76条查询结果，搜索用时 15 毫秒
41.
碳酸盐成岩作用的研究前沿和值得思考的问题 总被引：14，自引：0，他引：14
碳酸盐成岩作用在碳酸盐沉积学,尤其是在碳酸盐储层沉积学中具有十分重要的意义,近年在以下领域取得重要进展：（1）白云岩烃类储层的几何学和岩石成因学,尤其涉及到对已有白云化模式的评论和重新认识等。（2）碳酸盐储层热液改造的构造控制机理,涉及热液白云岩的成因及其对烃类储层的影响,尤其是深部热流体对碳酸盐成岩作用的影响。（3）对一些经典成岩理论的更新和对传统成岩理论的挑战,尤其是对混合水成岩作用带和对海水环境下的埋藏成岩作用的重新认识等。（4）锶同位素组成在海相碳酸盐研究中的广泛应用,涉及对地质事件的跟踪研究、海相地层的等时对比、定年和成岩过程中水一岩相互作用的研究等。然而,碳酸盐成岩作用研究中也存在一些问题值得我们思考：（1）深埋条件下碳酸盐最为重要的溶解介质可能是作为硫酸盐还原作用产物的H2S和CO2,但并非是温度越高,碳酸盐越溶解,相对较低的温度条件反而有利于溶解,这就是所谓的倒退溶解模式。（2）碳酸盐溶解需要有温度的降低（即必须要有足够的负△T）,这可通过两种途径实现：其一是沿断层向上运移的流体,显示断层等构造作用在碳酸盐成岩研究中的重要性;二是构造抬升,显示与构造有关的埋藏历史在碳酸盐成岩研究中的重要性。（3）控制白云石锶含量最为重要的因素是其晶体化学习性,锶在白云石中的较低的分配系数导致了白云岩普遍较低的锶含量,因此,我们不能仅利用白云岩的锶含量来判断白云化流体的性质,白云岩较低的锶含量也不能说明相应的白云化流体与海水无关。（4）与硫酸盐还原作用有关的SO4^2-的带出会诱发白云化作用或白云石的沉淀,而与硫酸盐溶解有关的SO4^2-的引入则会加速白云石的溶解。 相似文献
42.
Presence of gas hydrate and free gas in Iranian part of Makran accretionary prism changes the elastic properties of unconsolidated sediments and produces sharp bottom simulating reflectors (BSRs) which are observed on the 2-D seismic data. Different methods have been applied to estimate the gas hydrate and free gas saturations in marine sediments based on seismic measurements. Most of these methods are based on relating the elastic properties to the hydrate and free gas saturations and remotely estimating their concentration. In this regard, using the effective medium theory (EMT) which was developed for different modes of hydrate distribution is more considered among other rock physics theories. The main concern about saturation estimations based on EMT is that the velocities of the hydrate-bearing sediments primarily depend on how they are distributed within the pore space. Therefore, understanding the modes of hydrate distribution (at least cementing or non-cementing modes) is necessary to decrease the estimation uncertainties.The first intention of paper is to investigate amplitude variation versus offset (AVO) analysis of BSR to determine the hydrate distribution modes. The results from the probable saturation revealed that if the hydrate cements the sediment grains, BSR would show the AVO class IV and if hydrate does not cement the sediment grains, then BSR would show either the AVO class II or class III depending on the free gas saturation just beneath the BSR. The second intention of paper is to introduce some templates called reflectivity templates (RTs) for quantitative study of hydrate resources. These templates are provided based on the EMT to quantify the hydrate and free gas near the BSR. Validation of this approach by synthetic data showed that a reliable quantification could be achieved by intercept-gradient RTs, only if these attributes are determined with a high accuracy and good assumptions are made about the mineralogical composition and porosity of the unconsolidated host sediments. The results of this approach applied to a 2-D marine pre-stack time migrated seismic line showed that less than 10% of the gas hydrate accumulated near to the BSR in anticlinal-ridge type structure of Iranian deep sea sediments. The free gas saturation near to the BSR by assuming a homogeneous distribution was less than 3% and by assuming patchy distribution was about 3–10%. 相似文献
43.
针对天然气水合物沉积成矿因素不明确等问题,通过利用南海北部神狐海域的高分辨率三维地震、测井和岩心等资料,对晚中新世以来的地层进行了高分辨率层序划分和精细的沉积解释。从温压、沉积、构造等方面探讨了神狐海域天然气水合物分布的主控因素,认为：BSR上部附近处于水合物稳定温压范围内;粗粒沉积物有利于天然气水合物的富集;在含水合物层段内,孔隙度与天然气水合物饱合度成正比关系;滑塌体是天然气水合物赋存的有利相带;气烟囱形成过程中产生的断裂系统可为富含甲烷流体向上运移提供通道,并在其上部滑塌体富集成矿。因此,神狐海域具备天然气水合物成藏的优越条件,是天然气水合物勘探开发的有利区块。 相似文献
44.
西沙海槽研究区天然气水合物地球化学勘探及成藏模式研究 总被引：10，自引：0，他引：10
依据ODP204航次1250C站位钻井样品酸解烃数据结果,以及作者在南海西沙海槽研究区天然气水合物地球化学现场勘查中得到的多种烃类指标数据、异常点上微量甲烷碳同位素数值等资料,对海洋水合物地球化学勘探的依据和研究区气态烃异常特征、气体成因、天然气水合物成藏模式等相关问题进行了研究探讨。结果表明:气态烃指标地球化学异常主要分布在工区北部斜坡地带,并与BSR等地震标志及深部断裂关系密切;西沙海槽研究区海底沉积物气态烃甲烷以热解成因为主,但也有混合成因;推测该区天然气水合物为断层渗滤综合成藏模式。研究成果比较合理地解释了BSR分布和海底沉积物甲烷局部异常并非完全一致的原因;评价预测了该区天然气水合物有利勘探目标。成果为该区天然气水合物勘探、天然气水合物成因机制研究和天然气水合物远景预测,提供了地球化学方面的证据。 相似文献
45.
Abstract: The concentration of hydrogen sulfide gas (H2S) varies greatly in the oil-bearing basins of China, from zero to 90%. At present, oil and gas reservoirs with high H2S concentration have been discovered in three basins, viz. the Bohai Bay Basin, Sichuan Basin and the Tarim Basin, whereas natural gas with low H2S concentration has been found in the Ordos Basin, the Songliao Basin and the Junggar Basin. Studies suggest that in China H2S origin types are very complex. In the carbonate reservoir of the Sichuan Basin, the Ordos Basin and the Tarim Basin, as well as the carbonate-dominated reservoir in the Luojia area of the Jiyang depression in the Bohai Bay Basin, Wumaying areas of the Huanghua depression, and Zhaolanzhuang areas of the Jizhong depression, the H2S is of Thermochemical Sulfate Reduction (TSR) origin. The H2S is of Bacterial Sulphate Reduction (BSR) origin deduced from the waterflooding operation in the Changheng Oilfield (placanticline oil fields) in the Songliao Basin. H2S originates from thermal decomposition of sulfur-bearing crude oil in the heavy oil area in the Junggar Basin and in the Liaohe heavy oil steam pilot area in the western depression of the Bohai Bay Basin. The origin types are most complex, including TSR and thermal decomposition of sulfcompounds among other combinations of causes. Various methods have been tried to identify the origin mechanism and to predict the distribution of H2S. The origin identification methods for H2S mainly comprise sulfur and carbon isotopes, reservoir petrology, particular biomarkers, and petroleum geology integrated technologies; using a combination of these applications can allow the accurate identification of the origins of H2S. The prediction technologies for primary and secondary origin of H2S have been set up separately. 相似文献
46.
海洋天然气水合物的地球物理研究(Ⅳ):双似海底反射 总被引：2，自引：6，他引：2
由于双似海底反射可望指示一个动态演化的天然气水合物-游离气体系特征，这一重要问题的研究非常有意义。目前在世界上有两个双似海底反射分布区最为典型，一是挪威西部大陆边缘，另一个为东南海海槽大陆边缘，对双BSR的解释，主要有两种，一种是残留BSR，对应古温压条件下天然气水合物稳定带底界的反射，另一种是混合气体水合物沉积的底界反射。阐明双似海底反射层空间分布特征与其成因，建立动态演化的天然气水合物-天然气体系模型，可为深入了解天然气水合物形成机制、分布规律及其地质历史中的演变提供重要的科学基础。 相似文献
47.
Geochemistry of Peruvian near-surface sediments 总被引：6，自引：0，他引：6
Philipp Böning Michael E. Böttcher Cornelia Kriete Sven Lars Borchers 《Geochimica et cosmochimica acta》2004,68(21):4429-4451
Sixteen short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne. Solids were analyzed for major/trace elements, total organic carbon, total inorganic carbon, total sulfur, the stable sulfur isotope composition (δ34S) of pyrite, and sulfate reduction rates (SRR). Pore waters were analyzed for dissolved sulfate/sulfide and δ34S of sulfate. In all cores highest SRR were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and/or diffusion of sulfate from bottom water. δ34S of dissolved sulfate showed only minor downcore increases. Strong 32S enrichments in sedimentary pyrite (to −48‰ vs. V-CDT) are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction. Manganese and Co are significantly depleted in Peruvian upwelling sediments most likely due to mobilization from particles settling through the OMZ, whereas release of both elements from reducing sediments only seems to occur in near-coastal sites. Cadmium, Mo and Re are exceptionally enriched in WO sediments (<600 m water depth). High Re and moderate Cd and Mo enrichments are seen in BO sediments (>600 m water depth). Re/Mo ratios indicate anoxic and suboxic conditions for WO and BO sediments, respectively. Cadmium and Mo downcore profiles suggest considerable contribution to UEO/WO sediments by a biodetrital phase, whereas Re presumably accumulates via diffusion across the sediment-water interface to precipitation depth. Uranium is distinctly enriched in WO sediments (due to sulfidic conditions) and in some BO sediments (due to phosphorites). Silver transfer to suboxic BO sediments is likely governed by diatomaceous matter input, whereas in anoxic WO sediments Ag is presumably trapped due to sulfide precipitation. Cadmium, Cu, Zn, Ni, Cr, Ag, and T1 predominantly accumulate via biogenic pre-concentration in plankton remains. Rhenium, Sb, As, V, U and Mo are enriched in accordance with seawater TE availability. Lead and Bi enrichment in UEO surface sediments is likely contributed by anthropogenic activity (mining). Accumulation rates of TOC, Cd, Mo, U, and V from Peruvian and Namibian sediments exceed those from the Oman Margin and Gulf of California due to enhanced preservation off Peru and Namibia. 相似文献
48.
Auzende Jean Marie Van de Beuque Sabrina Dickens Gerald François Caroline Lavoy Yves Voutay Olivier Exon Neville 《Marine Geophysical Researches》2000,21(6):579-587
A recent swath-bathymetry and geophysical survey of the R/V L'Atalante in the Fairway Basin between Australia and New Caledonia allowed to confirm the Cretaceous age of the creation of the basin by continental stretching. This first stage of opening of the Fairway Basin is associated with the deposition of a continuous salt/mud layer feeding today numerous diapirs, some of them piercing the 3 to 4 km thick sedimentary cover and reaching the seafloor. In close link with this salt/mud layer a Bottom Simulating Reflector indicator of gas hydrates level occupies a 70000 km2 surface at about 500 to 600 m-depth beneath the sea floor. The coexistence of both BSR and diapirs suggests a thermogenic better than biogenic origin for the gas hydrates horizon. 相似文献
49.
南沙海域天然气水合物地震特征 总被引：5，自引：1，他引：5
南沙海域水深为200∽2500m，其中大于500m的水域约50万km^2，该区大部分区域发育沉积盆地，构造类型多样，具有形成天然气水合物的气源、温度及压力条件。根据地质及地球物理调查资料，分析了南沙海域天然气水合物成藏的地质条件及地球物理标志特征，认为南沙海域具备形成天然气水合物矿藏的条件，南沙海槽和南沙中部海域是天然气水合物形成的有利地区。 相似文献
50.
东海天然气水合物的地震特征 总被引：1，自引：0，他引：1
使用中国科学院海洋研究所“科学一号”调查船于2001年以及20世纪80年代在东海地区采集的多道地震资料,以海域天然气水合物研究为目的,对这些资料进行了数据处理并获得了偏移地震剖面。通过对地震剖面的解释,在6条剖面上确定了6段异常反射为BSR,均有振幅强、与海底相位相反的特点。6段BSR基本上都没有出现和沉积地层相交的现象。分析认为,这与东海地区第四纪以来的沉积特征有关,并不能由此否认这些异常反射是BSR。6段BSR出现的水深为750~2 000 m,埋深在0.1~0.5 s(双程时间)之间。随着海底深度的增大,BSR埋深有增大的趋势。计算结果显示,6段BSR所处的温度和压力条件都满足水合物稳定赋存所需要的温度和压力条件。本文的BSR主要与北卡斯凯迪亚盆地以及智利海域水合物的温度、压力条件相似,而与日本南海海槽、美国布莱克海台等海域水合物的温度、压力条件相差比较大。在地震剖面上,6段BSR所处的局部构造位置都和挤压、断层有关,有利于水合物的发育;在空间上,它们主要分布在东海陆坡近槽底的位置以及与陆坡相近的槽底。在南北方向上,除分布在吐噶喇断裂和宫古断裂附近外,还与南奄西、伊平屋和八重山热液活动区相邻。热液活动和水合物虽然没有直接的成因关系,但岩浆活动为水合物气源的形成提供了热源条件,为流体和气体的运移、聚集提供了通道条件,从而有利于水合物的发育与赋存。根据地震剖面反射特征推断,剖面A1A2和A14A23发育BSR的位置应该有气体或者流体从海底流出,可能是海底冷泉发育的位置。剖面A14A23上BSR发育处,振幅比的异常增大和BSR埋深的降低是相关联的。这种关联支持该处发育海底冷泉的推测。 相似文献