Research Of Sedimentary Facies And Reservoir Seismic Prediction Of Lacustrine Carbonate Reservoirs Of The Upper Es4 In Zhanhua Sag

With the development of petroleum exploration in Shengli oilfield,considerable oil-gas reserves have been found in lacustrine carbonate rocks.The reserves mainly distributed in the southeastern depression which is named Dongying sag,and with even low-level exploration in the northern part of the depression,Zhanhua sag.This paper presents a study on the lacustrine carbonates of the upper submember of the 4th member of the Eogene Shahejie Formation in the western Zhanhua sag,including Yidong,Luojia and Shaojia area.With the integrated application of geological and geophysical data,we learn carbonate sediment and reservoir develop distribution.The study area become the hot spot in exploration of Shengli oilfield in recent years because it's excellent structural and accumulation conditions.The lacustrine carbonate rocks of the studying area can be devided into three classes:limestone,dolomite and diamicitite.The limestone is the most important rock,including sandy limestone,micritic limestone and fram limestone.The dolomite distributing in limited area includes algal dolomite and micritic dolomite.The diamicitite distributing on the edge of the Zhanhua sag includes sandy limestone.The Upper 4th Member of Shahejie Formation in Shaojia Area is a third-order sequence,according to High-resolution Sequence Stratigraphy theory recognized three fourth-order sequence:C1,C2,C3.Sequence Stratigraphy division and correlation suggest that because of palaeogeomorphology and source systems,cycle preservation and composition are varied in different position of shaojia area.C3 cycle are poorly developed in the whole area,mostly develop in fan delta system of certain actic region,mainly preserved up hemicycle;C2 cycle is better developed,expect some high land areas of lake margin are dominated by erosion and only preserved up hemicycle.In C2 cycle,lacustrine carbonate are more developed in actic region while In gentle slope carbonate rock and clastic rock are mixed deposition;C1 cycle is best developed in shaojia area,owing to the compensating action of C3 and C2 cycle,carbonate rocks are widely developed in C1 cycle.Under the control of sequence straitigraphy,study depositional system distribution of lacustrine carbonate rock,result show that lake gemorphology,climate and material source play an important role in lacustrine carbonate deposition.In actic region,platform environment is common lacustrine carbonate facies including confine platform,platform algal mat,and platform algal reef.In gentle slope region recognized facies as followings:delt,mixed flat,mud flat,shallow algal mat.Building correct low-frequency model under the constraint of well log curves and selecting appropriate wavelet are very important to constraint sparse spike inversion.To achieve the best inversion results,the whole process is carried out under strict quality control which present how does the inversed model match the actual seismic data.Because of the carbonate reservoir in the research area is very thin and complex,so geostatistical inversion is choosen to explore the relation between wave impedance and favorable reservoir distribution.At last,sedimentary facies of researched area was predicted based on the analysis of the correlations between inverted impedance and well logging data and seismic attributes.