Research On The Sedimentary Facies Of Putaohua Oil Layer In The West Of Xingshugang-Gaotaizi Oilfield

Xingshugang-Gaotaizi study area is located in the wide and gradual anticlinal belt in Daqing placanticline of songliao basin,that is the third stage structural unit of the basin which is located in the central part of the central depression area.And it is the edge of transition of Daqing placanticline second stage structural unit to Sanzhao sag which included south of Xingshugang tectonic zone,Gaotaizi tectonic zone and Taipingtun tectonic zone.After forty years of development of the Putaohua oil layer in the study area,the main block has entered the highly water-bearing period,expansion of development zones and the optimization of evaluation area gradually become the focus to promote the increasing oil field reserves and productions.But in these blocks the formation thickness changes frequently,the lithology changes fast,oil and water distribution is very complex,in addition to the north and south strata division is not consistent,the differences between the main area and the edge area of sandstone on the east-west direction are very big.Therefore,it is necessary to study the sedimentary model of the shallow lake delta sedimentary system,to predict the favorable area and study the potential of the reservoir.Aiming at the above problem, this paper started from the development zone,with the high resolution sequence stratigraphy and reservoir sedimentology as a guide,and carried out the Putaohua reservoir stratigraphic division and correlation,reservoir sedimentary characteristics and distribution rules of sand body,sedimentary microfacies and evolution research,identified 7 sets of Lake flooding surface layer which controlled the high-resolution isochronic correlation of Putaohua oil layers.Finally established unified high-resolution isochronous stratigraphic framework of Putaohua oil layer in Xingshugang-Gaotaizi area and established the logging microfacies models of fluvial-dominated shallow water deltaic facies in Putaohua oil layer which included 1 sedimentary facies,3 subfacies and 13 microfacies.The fine dissection of sedimentary micro facies in the development zone of the dense well network showed that the Putaohua oil layer develops,sheet sand and mouth bar and so on.In the plane view sedimentary microfacies evolved from distributary channel, subaqueous distributary channel to subaqueous distributary and sheet sand,the width of distributary channel becomed narrower,the thickness becomed small,from broadband dendritic gradually to narrowband straight branched from north to South; vertically Putaohua oil layer vertical develop sedimentary evolution of sequence with first slowly then fast dereliction finally slowly transgression.Maximum dereliction is in PI32 layer,the area of sand body developmentis the largest,the erosion of rivers is strongest at this time.Secondary dereliction is in PI5 layer,the top and bottom of the putaohua oil layer are delta front delta subfacies and delta front subfacies which form effective reservoir-seal assemblages.The effect of sedimentation on the reservoir forming is mainly in 2 aspects:1) the vertical sedimentary evolution sequence of the Putaohua oil layer resulted in different reservoir types;2) sedimentary microfacies types caused large differences in rich sands productivity,distributary channel and subaqueous distributary channel becomed high-quality reservoir of oil enrichment. Finally according to the above research combined with structural information, identified 5 favorable target areas and pointed out the direction of the next increasing of oil field reserves and productions for the Putaohua oil layer in Xingnan region.