Reservoir Characteristics And The Comprehensive Evaluation Of He-8 Of Upper Paleozoic In East Of Yanchang

The study area is located in the Erdos Basin Yishan slope southeast of the Yanchang County East, the Objective layer is He-8, according to the sedimentary cycle and auxiliary sign layer from bottom to top He-8 can be divided into He-8 lower and He-8 upper. Based on logging, drilling, well-logging, oil testing data,data of experimental analysis and so on, using modern geological theory and various processing software, the author carries out the study of sedimentary stratigraphic correlation, the distribution of sedimentary facies and sandstone and comprehensive geological research of He-8 reservoir.Identify the He-8 sandstone reservoir and distribution space, establish the area He-8 reservoir evaluation comprehensive classification standard, thereby He-8 comprehensive classification and evaluation.The Stratigraphic thickness of He-8 lower and He-8 upper are stable, lateral variations are small. He-8 lower is thicker than He-8 upper. From east to west on a profile view, stratum is a west-dipping strata monoclinic, from west to east, stratum gradually rises.From north to south on the profile view, the change of northern to central is relatively flat, the southern region has been lifted, but the uplift rate lower than east and west, He-8 has developed long nose structure. He-8 is Delta front parfacies deposition, the provenance direction comes from the northeast, distributary channel and the subject of mouth bar which the formation of large and thick sand bodies is quality reservoir development. Lithology is mainly for the grain of lithic sandstone and small amounts of lithic quartz sandstone and quartz sandstone. He-8 reservoir is characterized by special low hole and Special low permeability, He-8 lower on the physical property is better than He-8 upper.Clay minerals are mainly for illite and small amounts of chlorite,kaolinite and Iraq/montmorillonite layer between,but have not smectite. Diagenesis is strong and the diagenetic evolution stage reached into “B” stage of late diagenesis period. Pore types maining with Lithic dissolved pores and feldspar dissolved pore contain intergranular pore, intergranular dissolved pore,intercrystalline pore,microcracks and so on.Composite types of microstructure consists of fine~small pore-fine throat. The reservoir has strong anisotropism. Reservoir thickness, porosity and permeability is controlled by sedimentary facies belt, has a certain direction.According to comprehensive classification evaluation standard of He-8 reservoir, there are a total of four types including Ⅰ, Ⅱ, Ⅲ, Ⅳ in He-8 reservoir, corresponding to good reservoir, medium reservoir, mainly poor reservoir, poor reservoir and mainning with Ⅲ,Ⅳ.