北礁凹陷中新统强振幅水道砂体含油气性探讨

Discussion on oil-gas bearing property of Miocene turbidite channel sandstones with high amplitude in Beijiao Sag, Qiongdongnan Basin

北礁凹陷首次在中新统发现大面积分布的具有强振幅反射特征的3套水道砂体,但对其含油气性至今未进行探讨。文中依据最新收集的三维地震资料和钻井资料,结合前人研究成果,探讨了这3套砂体的含油气性。研究表明:崖城组发育优质烃源岩且已处于生烃窗内,为砂体提供了丰富的气源;中新统三亚组底部、梅山组和黄流组底部分别发育3套强振幅水道砂岩,受底流(等深流)改造成为优质储层,其上覆千米级厚的泥岩,可形成良好盖层;多边形断层与构造断层提供了油气运移通道,与水道砂体共同形成有效的输导体系。由于北礁凹陷水道砂体和陵水LS17-2特大气田砂体的石油地质条件极为相似,以此推测3套强振幅水道砂体可能含有丰富的油气。

Three sets of turbidite channel sandstones with high amplitude were first found and widespreadly distributed in the Miocene in Beijiao Sag. Whether these sandstones contain oil and gas has not been discussed. Based on the latest 3D seismic data, drilling data, and literatures published, this paper first discusses the petroleum geological significance of these sandstones in detail. The resuhs show that high quality source rock is developed in Yaeheng Formation, which is within the window tor generating hydrocarbon, and provides hydrocarbon for these sandstones. Three sets of these sandstones within Miocene are developed in the bottom of Sanya and Huangliu Formations and within Meishan Formation, respectively, which, influenced by bottom currents （contour currents）, are potential high quality reservoirs covered by the kin-sealed nmdstone for cap rock. In the eireumstanee, they form a good assemblage for source rock, reservoirs, and regional cap rock. Vertical migration pathway for oil and gas generated from Yaeheng Formation is composed of combination of tectonic tauhs and polygonal tauhs, which form the good drainage system with channel sandstone. Furthermore, comparing Beijiao Sag with LS17-2 giant gas field in Lingshui Sag in the aspect of petroleum geology, we find both of them are extremely similar and three sets of channel standstones probably contain amount of hydrocarbon.