南海北部神狐海域天然气水合物分布的主控因素

CONTROLLING FACTORS OF NATURAL GAS HYDRATE IN THE NORTH OF SHENHU AREA,SOUTH CHINA SEA

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。

Studies of high-resolution sequence stratigraphy and sedimentology of the Upper Miocene of the Shenhu Area, northern slope of the South China Sea have been carried out by integrating 3D seis- mic data, well log data and core data. The main controlling factors over the distribution of gas hydrate in the area were discussed from temperature and pressure, sedimentation, structure and other aspects. We came to the conclusions as follows. The temperature and pressure near BSR is in the range of gas hydrate stability zone; the coarse-grained sediments is conducive to the formation of gas hydrates; po- rosity and gas hydrate saturation is directly proportional; the slump deposits are in favor of the gas hydrate enrichment; and the fractures generated in the process of the formation of gas chimney provid- ed the migration path for the methane-rich fluid moving upwards. It is concluded that the Shenhu area is a right target for exploration and development of gas hydrate because of its favorable conditions for gas hydrate accumulation.