西沙海域南部多边形断层的发现及其分布特征与控制因素

根据新采集的三维地震资料,在西沙海域南部发现了多边形断层,其发育分布具有层控特征明显、在富泥地层中发育、多方位走向、纵向断距小、平面延伸长度小且形态为不规则多边形等特征。由于研究区东西两侧应力条件的差异,导致多边形断层发育特征的差异明显。通过对多边形断层发育控制因素的分析,认为地层岩性(特别是西沙海域上构造层的远源细粒沉积物)是其发育的主控因素之一,同时水道砂岩、成岩作用及构造作用等也是影响其发育分布的因素。多边形断层可以作为流体运移的通道,它与下部构造断层连接可将深部烃源岩中的油气运移到上部储层中聚集,或继续向上运移到浅部地层中形成天然气水合物。

Characteristics of Polygonal Faults Distribution and Analysis of Its Controlling Factors in Southern Xisha Offshore,South China Sea

The polygonal faults in southern Xisha Offshore, South China Sea, were first discovered. On the basis of the 3D seismic data and the analysis of the controlling factors for polygonal faults development, it is concluded that the fine grained sediment strata from far source is the favorable development site in upper structure layer of Xisha Offshore. At the same time, channel sandstone, diagenesis and tectonism affected their development and distribution. Polygonal faults, combining with the deep tectonic fault, provided channels for fluid migration from deep hydrocarbon source rocks to the upper reservoir, or continued upward to the shallow strata to form natural gas hydrates.