The Reservoir Prediction Research Of Lower Xiaganchaigou Formation In Xiandong Region,Northern Qaidam Basin

Maxin region,in northern margin of Qaidam Basin,is an important hydrocarbon-bearing block.A number of oil and gas fields have been found in the high position of the structure,in recent years three exploratory wells which have been drilled in Xiandong-Xianbei slope have oil and gas shows.Industrial oil and gas was obtained in mx4 well at the slope of Maxi and low-yield gas was obtained in xmshen 5 well,the Xianganchaigou formation is the main hydrocarbon bearing layer.In this paper,the reservior characteristics in Xiandong region are studied by single well data,geological data and seismic data,trying to predict the favorable reservoir distribution,as a result,it provides the dependence for advanced exploration.The research shows that the Lulehe Formation and Lower Xiaganchaigou Formation can be divided into a complete 3th-order sequence and the Lower Xiaganchaigou Formation can be divided into three 4th-order sequence;the electrical characteristics of the reservoir are low SP,low GR and low impedance.Seismic attribute analysis and seismic inversion shows that,in E₃¹ transgressive system,low impedance sand bodies which have wide range of distribution are mainly concentrated in Xianbei slope area and the southwest slope of xd1 well,xd2 well;the sand bodies of the E₃¹high system tract are mainly concentrated on the slope of xd2 well area,and have narrow distribution.Based on the comprehensive analysis of the drilling wells and inversion results in the work area,it is considered that the formation of reservoir caprock in the study area of E₃¹-HST can form an effective lateral occlusion layer,which is a favorable oil and gas accumulation area.The main reservoir areas in the study area are located in the lower part of the southern Xiangdong slope and Xianbei slop.