Characteristics of pore evolution and its controlling factors of Chang 6 reservoir in Y area of Ansai oilfield

Using ordinary thin sections,casting thin sections,SEM,X-ray diffraction,high pressure mercury and other technical means to study on pore characteristics of Chang 6 reservoir in Ansai oilfield, Ordos basin,and then combined with the sedimentary environment、lithologic feature and diagenetic evolution of the reservoirs to analyse deeply the factors that affected the reservoir porosity . The result shows that the lithologic of Chang 6 reservoir is mainly of feldspar fine sandstone;The main pore types of the reservoir include dissolution pores and residual intergranular pore;Diagenetic evolution has reached late diagenetic A stage;Depositional environments and diagenesis are major factors of reservoir porosity. Different sedimentary microfacies direct effect the degree of the composition maturity and structure maturity of the reservoir sandstones. Compaction is the main factors of pore reducing;on the one hand,the cementation of carbonatite and laumonite reduce the intergranular porosity,on the other hand, support the frame. and enhance the ability to resist compaction. Furthermore, it can provided space and material for the dissolution of secondary pores in the later. In addition, the dissolution changing the pore structure, making secondary pore development.