Sedimentary microfacies research of He-3 member Ⅵ-Ⅶ oil group in Bidian area of Biyang depression

By using core,drilling,well logging and analysis of testing data,through rock facies and logging facies analysis,combined with the rock structure feature and phase sequence,the sedimentary microfacies research ofⅥ-Ⅶ oil group in He-3 member of Bidian area,Biyang depression has been carried out.Located in multiple provenances intersection area,the area ofⅥ-Ⅶoil group in He-3 member has developed four sedimentary systems,namely delta,fan delta,lacustrine and underwater gravity,further can be divided into six subfacies,namely delta front,front delta,fan delta front,fan delta,shallow lacustine and mid-deep lacustrine.In order to make a distinguish between delta front and microfacies of fan delta front,the delta front is divided into four kinds of microfacies,namely underwater distributary channel,river mouth bars,delta branch bay and distal bar.The fan delta front is divided into four kinds of microfacies,namely underwater distributary channel,frontier sand,tributary bay of fan delta and sand sheet.The sand bodies in the north and northwest of delta front underwater distributary channel and underwater distributary channel sand bodies in the south are thicker.In deep depression,the delta front far bar,fan delta front,and sheet sand have been mainly developed,with thinning sand body thickness.In vertical direction,it is mainly with retrogradation deposits,the sand body distribution range ofⅦ oil group is wider than that ofⅥ oil group.The physical properties of delta distributary channel,distal bar,fan delta underwater distributary channel,frontal sand,sand sheet and underwater gravity flow are good,therefore,acting as favorable exploration target in the area.