The diagenesis of Chang 8 reservoir sandstone and its effect on reservoir quality in the Heshui region

Aim Through researching on diagenesis of Chang 8 reservoir sandstone in the Heshui region of Ordos Basin,it could find the reasons of low permeability and porosity,and fulfill prospect and evaluation of those zones where the high quality reservoirs are developed. Methods Based on the sedimentary facies research,using the microscope and the scanning electronic microscope,it is analyzed at diagenetic microscopic feature. Results The sandstones of Chang 8 sandstone is divided into six diagenetic lithofacies:mica intensive compaction,carbonate cement facies,feldspathic solution facies,kaolinite cement facies,chlorite remnant intergranular pore facies,chlorite remnant intergranular pore-feldspathic solution facies. Conclusion Sandstones in the latter two facies belts in the core of the mainsandbody have good poroperm characteristics and oil-bearing properties,thus they are favorable forhydrocarbon accumulation.