Research of Sedimentary Facies of the IntervalII of the 3~(rd) Member of Liushagang Formation in WZ10-3 Oilfield and Surrounding Areas

On the basis of core observation and description,combined with analysis of logging data,the sedimentary facies of the intervalⅡ of the 3rd Member of Liushagang Formation is identified by comprehensive analysis of 3sedimentological markers of rock colours,rock types and sedimentary structures,sub-facies and microfacies are divided.Then,sedimentary facies distribution and sedimentary evolution rule of the intervalⅡare discussed.The results indicate that fan delta-lacustrine depositional system is identified in the intervalⅡ,and it is further divided into 4sub-facies of fan delta plain,fan delta front,pro-fan delta and shallow lake,and some microfacies.Fan delta is widely developed in the northwest of the study area during the depositional period of the intervalⅡ,while the shore-shallow lacustrine sub-facies is restricted to the southeast part of the study area.From the depositional period of MSC5to MSC6of the intervalⅡ,the pattern of sedimentary facies distribution is similar,but the distribution range of fan delta of MSC6depositional period is continuously reduced with the gradual rising of lacustrine level.Fan delta front sandbody is the favorable oil and gas reservoir facies belt.