Reservoir Diagenesis and Porosity Evolution Characteristics of Chang 6 Reservoir in the Eastern Ansai Oilfield

By comprehensive use of techniques of physical property analysis and high pressure mercury,cast thin section,scanning electron microscope,Chang 6 reservoir in the eastern Ansai Oilfield is studied.The results show that Chang 6 reservoir is of poor physical property,pore throat is small with powder feldspar sandstone,complex clastic composition,low compositional maturity and low to moderate textural maturity.Original pore space of reservoir is missed by compaction,cementation destroys part of the primary porosity and secondary porosity,the dissolution improves the reservoir properties.By dividing the diagenetic sequence,based on the impact of diagenesis on reservoir properties,reservoir porosity evolution is analyzed,it indicates that early porosity is 34.96% in 6 reservoir,currently it is 11.01%.