Dynamic accumulation of gas hydrates associated with the channel-levee system in the Shenhu area, northern South China Sea
Dynamic accumulation of gas hydrates associated with the channel-levee system in the Shenhu area, northern South China Sea
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南海北部神狐海域与河堤系统相关的天然气水合物动态聚集
DOI：
10.1016/j.marpetgeo.2020.104354
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发表时间：
2020-07
影响因子：
4.2
通讯作者：
Lin Lin
中科院分区：
文献类型：
--
作者：
Zhang Wei;Liang Jinqiang;Wan Zhifeng;Su Pibo;Huang Wei;Wang Lifeng;Lin Lin
研究海底河道系统及其伴生含气流体的形成和分布，对天然气水合物勘探具有重要意义。在南海北部中国北部深湖地区，从相当于河道-堤防系统堤防的海底海脊中回收了饱和度高达65%的浸染型天然气水合物。海底海脊沉积沉积以细粒粉砂和富粘土粉砂为主，饱和度较高的天然气水合物优先聚集在粘土含量较少的较粗沉积物中。尽管丰富的有孔虫化石可能增加了储集层的孔隙空间，但它们的存在并不是高饱和度水合物的必要条件。高饱和度水合物对应的储集层中黄铁矿含量较高，说明甲烷充足的还原环境为高饱和度水合物的形成提供了充足的天然气。由于河道-堤防系统的迁移，不同的河道形成了各自的沉积体系，包括河道充填、埋藏河道充填、冲刷沟槽和坍塌浊流。在河道填充物和堤防中发现了相对粗粒的沉积物，水合物的聚集受沉积物的岩性及其与天然气水合物稳定带(GHSZ)的空间耦合作用的影响。基于现场测量的GHSZ模拟表明，侵蚀和沉积以及地温梯度的变化导致了似海底反射体(BSR)的向上/向下迁移。在河道侵蚀侧，地层变薄，快速侵蚀可能破坏浅层BSR，导致天然气水合物分解和甲烷释放，并可能导致浊流坍塌和渗流；而在河道沉积侧，地层增厚。河道-堤防系统中的BSR将逐渐向新的GHSZ移动，最终形成新的BSR；在原始P-T条件下形成的BSR的部分保留，地震剖面中出现双BSR。通过气体烟囱向上移动的热流体也可能导致了GHSZ的迁移，导致了双BSR的出现。在河道横向运移和含气流体垂向运移过程中，GHSZ与河道冲刷沉积过程之间存在动态调整关系，导致深湖地区水合物动态聚集。建立了河道运移与BSR变化关系的模型，对认识天然气水合物的形成和聚集机制具有重要意义。
Research on the formation and distribution of submarine channel systems and associated gas-bearing fluids is of great significance for gas hydrate exploration. Disseminated gas hydrates with high saturation up to 65% were recovered from a submarine ridge, equivalent to the levee of the channel–levee system in the Shenhu area, northern South China Sea. Sedimentary deposits in the submarine ridge were dominated by fine-grained silt and clay-rich silt; gas hydrates with relatively high saturation preferentially accumulated in coarser sediments with less clay content. Although abundant foraminifera fossils may have increased reservoir pore space, their presence was not a necessary condition for high-saturation hydrates. Higher levels of pyrite appeared in the reservoirs corresponding to high-saturation hydrates, which suggests that the reducing environment caused by sufficient methane provided adequate gas to form higher-saturation hydrates. Because of the migration of the channel–levee system, different channels formed their respective depositional systems composed of channel-filling, buried channel-filling, erosion grooves, and slumped turbidities. Relatively coarse-grained deposits were identified in the channel fillings and levees, and the accumulation of hydrates was affected by the lithological features of the sediments and their spatial coupling with the gas hydrate stability zone (GHSZ). GHSZ modeling based onin situmeasurements indicated that erosion and sedimentation, as well as variations of the geothermal gradient, resulted in the upward/downward migration of bottom simulating reflectors (BSRs). On the erosion flank of the channel, the strata thinned, and rapid erosion was likely to destroy the shallower BSR, causing gas hydrate decomposition and methane release, and may have caused turbidite slumping and seepage, whereas the strata thickened on the deposition flank of the channel. The BSR in the channel–levee system would gradually move toward the new GHSZ, eventually forming a new BSR; parts of the BSR that formed under the original P–T conditions have remained, and double BSRs occurred in the seismic profile. The thermal fluid that moved upward through a gas chimney may also have caused the migration of the GHSZ, resulting in the emergence of double BSRs. During the lateral migration of the channel and the vertical migration of the gas-bearing fluid, there was a dynamic adjustment relationship between the GHSZ and the erosion–deposition process of the channel, resulting in the dynamic accumulation of hydrates in the Shenhu area. A model to demonstrate the relationship between channel migration and variation of the BSR was established, which is of great significance for understanding the formation and accumulation mechanisms of gas hydrates.
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影响因子：
3.7
作者：
A. Peketi;A. Mazumdar (corresponding author);R. K. Joshi;D. J. Patil;P. L. Srinivas;A. M. Dayal
通讯作者：
A. Peketi;A. Mazumdar (corresponding author);R. K. Joshi;D. J. Patil;P. L. Srinivas;A. M. Dayal
影响因子：
5.3
作者：
Haacke, R. Ross;Westbrook, Graham K.;Hyndman, Roy D.
通讯作者：
Hyndman, Roy D.
南海神狐海域天然气水合物分布及特征
影响因子：
4.2
作者：
尉建功
通讯作者：
尉建功
DOI：
10.3724/sp.j.1140.2011.05095
发表时间：
2011
期刊：
Marine Geology & Quaternary Geology
影响因子：
--
作者：
Wang Jinlian
通讯作者：
Wang Jinlian
影响因子：
3.5
作者：
C. Gong;Yingmin Wang;Weilin Zhu;Weiguo Li;Qiang Xu
通讯作者：
C. Gong;Yingmin Wang;Weilin Zhu;Weiguo Li;Qiang Xu