Depositional characteristics and accumulation model of gas hydrates in northern South China Sea
Depositional characteristics and accumulation model of gas hydrates in northern South China Sea
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DOI：
10.1016/j.marpetgeo.2014.03.011
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发表时间：
2014-09
影响因子：
4.2
通讯作者：
Xinghe Yu;J. Wang;Jinqiang Liang;Shunli Li;X. Zeng;Wen Li
中科院分区：
文献类型：
--
作者：
Xinghe Yu;J. Wang;Jinqiang Liang;Shunli Li;X. Zeng;Wen Li
南海具有天然气水合物成藏的有利条件和勘探前景。南海海底模拟反射层（BSRs）分布广泛。利用地震和层序地层学方法，确定了晚中新世以来沉积的三个层序中BSR的空间分布。通过对南海北方天然气水合物成藏的气源条件、运移通道、热流值、赋存特征、沉积条件（包括沉积相、沉积速率、砂含量、岩性等）和沉积体（构造斜坡、滑塌块体、沉积波）的综合分析，系统地研究了南海北部天然气水合物成藏特征。这项研究表明，特定的地质控制是重要的存在的BSR在SCS中，没有那么多的基本热力学控制，如温度，压力和气源。在此基础上，建立了典型的沉积-聚集模式。该模式概括了陆棚、陆坡和陆脊各沉积体系的分布，并给出了天然气水合物成藏的典型要素。BSR通常出现在坡折带、深水重力流和等深流中。深沪钻井区天然气水合物沉积物多为粉砂或粘土，粉砂含量约70%。在陆架区，海底反应带横向连续，天然气输运和运移条件是天然气水合物形成和聚集的关键。在大陆坡，大多数海底地震带都与起伏陡峭的地形带有关，这些地形带具有长期的隆起和沉降交替。沉积物的快速卸载为天然气水合物提供了有利的沉积储集空间。在大陆隆起区，海底扇、浊流等沉积物中存在BSR。
The South China Sea (SCS) shows favorable conditions for gas hydrate accumulation and exploration prospects. Bottom simulating reflectors (BSRs) are widely distributed in the SCS. Using seismic and sequence stratigraphy, the spatial distribution of BSRs has been determined in three sequences deposited since the Late Miocene. The features of gas hydrate accumulations in northern SCS were systematically analyzed by an integrated analysis of gas source conditions, migration pathways, heat flow values, occurrence characteristics, and depositional conditions (including depositional facies, rates of deposition, sand content, and lithological features) as well as some depositional bodies (structural slopes, slump blocks, and sediment waves). This research shows that particular geological controls are important for the presence of BSRs in the SCS, not so much the basic thermodynamic controls such as temperature, pressure and a gas source. Based on this, a typical depositional accumulation model has been established. This model summarizes the distribution of each depositional system in the continental shelf, continental slope, and continental rise, and also shows the typical elements of gas hydrate accumulations. BSRs appear to commonly occur more in slope-break zones, deep-water gravity flows, and contourites. The gas hydrate-bearing sediments in the Shenhu drilling area mostly contain silt or clay, with a silt content of about 70%. In the continental shelf, BSRs are laterally continuous, and the key to gas hydrate formation and accumulation lies in gas transportation and migration conditions. In the continental slope, a majority of the BSRs are associated with zones of steep and rough relief with long-term alternation of uplift and subsidence. Rapid sediment unloading can provide a favorable sedimentary reservoir for gas hydrates. In the continental rise, BSRs occur in the sediments of submarine fans, turbidity currents.