Reservoir Characteristics And Main Controlling Factors Of Chang-8 Reservoir Group In The East Side Of Xifeng

In the thesis,chang-8 reservoir group in the east side of Xifeng area as the research object,by drilling core observation and description,thin section observation and identification,and SEM,pore permeability test,X-ray diffraction and mercury intrusion analysis of laboratory data.Combined with the previous research results and theoretical analysis,the sedimentary facies and reservoir characteristics of the chang-8reservoir group in the study area are studied,and the main controlling factors of the reservoir are analyzed.A large amount of core data shows that the chang-8 reservoir group in the east side of Xifeng is mainly composed of a set of interbedded gray fine-medium-grained sandstone with dark gray siltstone and mudstone,and in partial area has the lithologic combination of partially sandwiched thin coal or coal line.According to sedimentary facies signs such as sedimentary structure,paleontology fossils and logging curves,it is determined that the chang8 oil formation in the east of xifeng area mainly develops shallow delta-lake facies,which can be divided into 4 subfacies and 12 microfacies.The reservoir characteristics in the study area were studied by casting thin section and SEM.In the east of Xifeng area,The chang-8 sandstone has a high feldspar content on the whole.The rock types are mainly lithic arkose and feldspar lithic sandstone,and a few are arkose.There are many types of pores,and residual primary intergranular pores are the most important storage space,followed by secondary dissolution pores and micro-fractures.The main diagenesis types include compaction,cementation,metasomatism and autogenetic mineral filling.The porosity of chang-8₁ and chang-8₂oil formations is mainly 4%to 12%,and the permeability is mainly 0.01×10^-3?m to0.5×10^-3?m.Both of them are relatively low and have poor correlation between porosity and permeability.Combined with the characteristics of their reservoir space,it is determined that they are mainly fracture-porosity reservoirs.The sand body of chang 8 mainly develops four types of sand body structure,and the sand body structure characteristics are closely related to the physical properties of the reservoir.The continuously superimposed thick sand body usually has high porosity and permeability,while the lenticular sand body is generally densified due to calcareous cementation.The reservoir of chang-8 reservoir group in the study area are mainly controlled by sedimentary facies,diagenesis and tectonics.The sedimentary facies mainly controls the spatial distribution of sand bodies and the original physical properties of sandstone,while diagenesis and tectonism transform the reservoir sandstone and determine the ultimate properties of the reservoir to a large extent.Diagenesis has the most critical influence on the reservoir,among which compaction,autogenetic mineral filling and cementation except chlorite ring edge are all destructive to the reservoir.The circumferential cementation of chlorite is an important constructive diagenesis.Fractures associated with tectonics can form a large number of micro-fractures,especially in the south of the study area,which is an important type of reservoir space.Reservoir evaluation results show that the main channel development area with continuous superimposed sand bodies is usually the most favorable sedimentary facies belt.