南海北部神狐海域深水水道演化与水合物成藏的关系

The interaction mechanism of bottom current and gravity current in Shenhu deep-water channels is generally accepted by researchers, however, the formation and accumulation progress of gas hydrate in this area is still controversial. Rare studies have reported the potential relationships between the evolution of channels and the formation and accumulation of gas hydrate. As a consequence, this study will try to establish a multi-stage interaction depestional model of bottom current and gravity current based on the detailed interpratation of seismic data in Shenhu area，and then numerical simulation work will carried out. This study also aims at restore the evolution history of the migration channels in Shenhu area, to reveal the relationship between the interaction of bottom current and gravity current and evolution of subsuface fluid field, and to reveal the relationship between channels’ migration and gas hydrate accumulation. This study will be of great assistance in towards understanding the reasons of gas hydrate accumulation mechanism in Shenhu area and providing a reference for the world's deep-water channel type gas hydrate research.

神狐深水水道底流与重力流交互作用机制得到了普遍认可，但本区水合物成藏模式分歧较大，水道的演化和水合物的成藏关系不清，国内外对此研究较少。针对该问题，拟进行神狐地震资料精细解释，建立多期底流与重力流交互沉积模型、开展数值模拟工作。通过本项目可达到以下目的：1).恢复神狐海域迁移水道的时空演化史；2). 揭示底流与重力流交互作用与地下流场演化之间的关系；3). 厘清水道迁移与水合物成藏之间的关系。研究结果有助于完善神狐水合物成藏模式，为全球水道型水合物研究提供借鉴，具有重要的科学意义和应用价值。

通过对神狐海域三维地震资料的综合解释，选取过SH-7井地震剖面，结合前人研究恢复了该剖面的岩性、古水深、热流分布、孔隙度、渗透率等参数。利用basin2软件和生物成因天然气水合物成藏动力学模拟系统(Hydrate Dynamics)，分别对以下4组实验开展二维数值模拟研究：A，热流值横向均一分布无垂向裂隙；B，热流值横向均一分布有垂向裂隙；C，热流值横向差异分布无垂向裂隙；D，热流值横向差异分布有垂向裂隙。结果表明：D组实验水合物赋存深度、饱和度与钻探结果最为相近，综合认为地形高部位的低热流值与垂向高渗透性裂隙两个因素共同控制了本区水合物成藏，地形高部位是水合物勘探的有利区带。.本研究对水合物勘探和开发都具有重要的启发意义，即：高饱和度的水合物分布在地形高部位的下方，高部位以下的水合物稳定域会形成类似背斜圈闭的构造，有利于下伏游离气的聚集和水合物的形成，是水合物勘探开发的有利区。