南黄海盆地南五凹古近系戴南组沉积相及储盖组合分析

Sedimentary Facies and Analyze on Reservoir-seal Assemblage of the Dainan Formation of Paleogene in Nan 5 sag,Nanhuanghai Basin

南五凹是南黄海盆地南部坳陷最具勘探潜力的凹陷之一,是一个南断北超的典型箕状断陷湖盆,其中古近系戴南组为河湖相砂泥岩地层。综合应用测井、岩心、地震剖面等资料,共识别出3种主要的沉积体系:三角洲、湖泊、扇三角洲沉积体系,其基本继承了南部物源为主的沉积格局,北部三角洲不太发育,凹陷中部为滨浅湖相沉积。沉积相在平面上分布范围明确,纵向上既有差异性又有继承性。戴南组发育三套储盖组合,从矿物成分、实测孔隙度及砂岩厚度看储层发育,由丰富的油气显示体现了盖层的有效性,最有利的储盖组合是戴一段下部的组合。

The Nan 5 Sag is one of the most important potential oil and gas exploration areas in the south depression of Nanhuanghai basin,and is a typical dustpan shaped subsidence lacustrine basin with a fault as its south boundary and a slope to the north.The Dainan formation in the Nan 5 Sag is mainly comprises fluvial-lacustrine sandstone and mudstone.Based on data of log,core and seismic profile,There are three kinds of sedimentary systems,including delta,fan delta and lacustrine system,fan delta in the south fault is the main provenance inheritance,delta in the north is restricted,shallow lacustrine system is the largest area in the depression.The sedimentary facies were developed in specific places in plane and shows differences and inheritance in vertical evolution.There are three reservoir-seal assemblages in Dainan formation.The mineral composition,porosity and sandstone thickness show that the reservoir is good.The presence of oil and gas show that the seal is availability,where the best reservoir-seal assemblage is the lower member of Dainan formation.