西湖凹陷平湖组基于沉积相标志的沉积特征研究

Study on sedimentary characteristics of the Pinghu Formation based on sedimentary facies markers in Xihu Sag, East China Sea Basin

针对东海盆地西湖凹陷平湖组沉积相类型不清的现状,本文结合粒度分析、测录井等技术手段,通过对西湖凹陷平湖组29口井沉积相研究,将平湖组划分为3种沉积相及7种亚相并建立沉积模式。综合研究认为:平湖组沉积时期发育海陆过渡的沉积体系,主要包括潮控三角洲、潮坪和海湾等沉积相,进一步划分为三角洲平原、三角洲前缘、前三角洲、潮上带、潮间带、潮下带和半封闭海湾等7种亚相;西部斜坡带沉积相以潮坪为主,潮间带范围最大,由物源供给、河流注入形成多个潮控三角洲,中央洼陷带沉积相主要为半封闭海湾亚相。

The status of sedimentary facies in the Pinghu Formation of Xihu Sag,East China Sea Basin,is unclear.Based on particle size analysis and mud logging technology,29 wells were studied and sedimentary facies models were established.The sedimentary facies of the Pinghu Formation in the study area were divided into three sedimentary facies and seven subfacies.A study of the depositional system in the Pinghu Formation revealed the following subfacies:transitional,mainly including tidal delta,tidal flat and bay,further divided into delta plain,delta front and prodelta;supratidal zone;intertidal zone;subtidal zone;and semi-enclosed bay.In addition,we found that:(1)the tidal flat sedimentary phase is mainly in the west slope belt,where the tidal range is the largest;(2)the formation of multiple tidal deltas constitutes the source of supply;and(3)the sedimentary facies is mainly in the central sag zone of the semi-closed bay facies.