东海西湖凹陷P油田古近系始新统沉积模式及油气地质意义

The Sedimentary Model of Paleogene-Eocene in P Oil Field of Xihu Sag of East China Sea Basin and the Petroleum Geologic Significance

基于岩心、薄片、测井、地震等多种资料,对西湖凹陷P油气田古近系始新统沉积模式进行研究,建立了滨岸–受潮汐影响的三角洲–潮坪的沉积演化序列。P油田始新统包括宝石组和平湖组地层,其中宝石组与下伏潜山不整合接触,沉积相为滨岸砂沉积,砂体围绕古凸起呈环带状连片分布,沟谷处砂体厚度大,梁或脊部位砂体厚度薄。同时,宝石组岩石组分受母岩岩性控制明显,其中母岩为花岗岩和石英变质岩的富石英岩屑砂岩储层物性最好。平湖组整合沉积于宝石组地层之上,平湖组下部地层为受潮汐影响的三角洲沉积,砂体厚度大,分布连片。平湖组中–晚期逐渐演变为潮坪沉积,以窄小河道沉积为主。宝石组地层超覆于潜山基底之上,形成地层超覆油气藏。平湖组潮坪窄河道沉积主要受岩性控制,形成岩性油气藏。

Based on core, thin section, well logging and seismic data, the Eocene sedimentary model of P oil and gas field in Xihu sag is studied, and the sedimentary evolution sequence of shore deposit-tidal delta-tidal flat is established. The Eocene of P oilfield consists of Baoshi formation and Pinghu Formation. The Baoshi formation is unconformably contacted with the underlying buried hill, and the sedimentary facies are shore sand deposit. The sand body is distributed in a ring belt around the ancient uplift, the sand body at the gully is thick, and the thickness of sand body in ridge or beam is thin. At the same time, the rock composition of Baoshi formation is obviously controlled by the lithology of parent rock. The Pinghu Formation is integrated and deposited on the Baoshi formation. The lower part of Pinghu Formation is delta deposit affected by tide. The sand body is thick and distributed continuously. The Pinghu Formation gradually evolved into tidal flat deposits in the middle and late stages, mainly in narrow channel deposits. The Baoshi formation overlies the basement of buried hill, forming stratigraphic overlap reservoir. The tidal flat narrow channel deposits of Pinghu Formation are mainly controlled by lithology, forming lithologic reservoirs.