西湖凹陷平湖组岩相类型及沉积相分析

Lithofacies types and sedimentary facies of Pinghu Formation in Xihu Depression

西湖凹陷平湖组沉积相资料比较单一、研究区域相对局限,对其沉积相类型、展布特征及沉积模式等的认识不清。对西湖凹陷46口平湖组取心井进行岩心观察,根据粒度和沉积构造等的不同来划分岩相,然后根据岩相的成因类型、组合特征及测井曲线特征等来划分沉积相,将平湖组岩相划分为砾岩相、砂岩相和细粒岩相3种类型,并认为平湖组主要发育受潮汐作用影响的三角洲相、潮坪相及局限浅海相等沉积相,并细分出三角洲平原、三角洲前缘、前三角洲、潮上带、潮间带、潮下带、陆架砂脊及陆架泥等亚相。综合考虑平湖期不同时期的区域构造运动、古地貌形态及物源供应等影响因素,建立了西湖凹陷平湖期箕状断陷和潮汐作用控制下的物源-沉积模式,为储层研究奠定了基础。

The research on sedimentary facies of Pinghu Formation in Xihu Depression is relatively limited, and the types of sedimentary facies, distribution characteristics and sedimentary model are unclear. Based on grain size and sedimentary structures of cores from 46 wells, the lithofacies of Pinghu Formation was identified. Then according to genetic types of lithofacies, lithofacies assemblage characteristics and well logging features, the sedimentary facies of Pinghu Formation was identified. The lithofacies was divided into three types： conglomerate facies, sandstone facies and fine-grained facies. The main sedimentary facies are tidal delta, tidal fiat and confined shallow marine, which can be divided into several subfacies including delta plain, delta front, prodelta, supratidal zone, intertidal zone, subtidal zone, and shelf sand ridge etc. Considering the influencing factors such as the regional tectonic movement, palaeogeomorphology, provenance supply at the different Pinghu stage, the provenance-sedimentary model both controlled by half graben and tidal action of Pinghu Formation in Xihu Depression was established, which provides the base for further reservoir research.