Study On Architectural Heterogeneity Characteristics Of Cretaceous Reservoir In Keshen Area,Kuqa Depression

Reservoir structure heterogeneity is objective,a combination of single or multiple attributes difference in a particular space.It is mainly controlled by sedimentation,affecting the direction of fluid flow inside the reservoir and other factors,which leads to the diagenetic evolution of the reservoir and the differences in hydrocarbon accumulation processes.The study area is located in Keshen area,Kuqa depression in the north part of Tarim Basin.Cretaceous developed Bashijiqike Formation,Baxigai Formation,Shushanhe Formation and Yageliemu Formation from the top to the bottom,and the Bashijiqike Formation is the target.Based on the establishment of the stratigraphic framework,the architectural heterogeneity of reservoir is studying.Because the sedimentary system controls the distribution of sandstones bodies and mudstone,the development of reservoir heterogeneity is determined.Therefore,starting from the sedimentary characteristics and sedimentary facies,the single well phase is established by analyzing the core data and logging data.The sedimentary facies of the first and second sections of the Bashijiqike Formation are braided river delta front facies,The dominant sedimentary facies is the subaqueous distributary channel,interdiatributary bay and point channel bar.The architectural heterogeneity in the microfacies scale is reflected in the same microfacies with different rock combination types.The most common rock combination types are thin mudstones in thick sandstones and sand-mud interbed.The heterogeneity of the single sandstone body to the sandstone group is characterized by interlayers.Three interlayers are developed,which are mud,petrophisical,and calcareous interlayers.It is observed that the mud interlayers are generally developed between the sandstone bodies or inside the sandstone bodies.The calcareous interlayers are developed inside the sand body,which usually at the bottom of the sandstone bodies.There are two kinds of physical interlayers,the first one is between the sandstone bodies and the other is at the bottom of the sandstone bodies,which is coarse.In order to characterize the development of the interlayer on the plane,the interlayer density parameter(D_k)is choosed and the D_kmapping of different sections of the Bashijiqike formation are made.By studying the physical properties of reservoirs,the distribution of planes and profiles is analyzed.Combined with the interlayer density,porosity,permeability and sedimentary facies,the development zone of favorable reservoirs is obtained.By establishing sedimentary simulation model of the study area,the basin evolution is related to reservoir development,and the formation mechanism of reservoir structure heterogeneity is analyzed.By studying the distribution characteristics and formation of reservoirs under different levels,it is concluded that the heterogeneity of the reservoir in the Bashijiqike Formation in the study area is weak in the eastern and western part,strong in the middle part.The heterogeneity of the second member reservoir of the Bashijiqike Formation is strong in the middle and western part,weak in the eastern part;in the profile,the heterogeneity of the first member of Bashijiqike is stronger than that of the second member of Bashijiqike Formation;the heteneogrneity is controlled by sedimentary facies,which provide a theoretical basis of diagenesis differences and accumulation processes in the later stage.