Succession of diagenesis and pore in sandstone reservoirs in Jiyuan Oilfield

Aim To ascertain Ascertain the control of diagenesis on reservoirs quality of the Yanchang sandstone,Jiyuan Oilfield.Methods Multiple analysis methods were adopted,including coloration and casting slice identification of sandstone,scan electron microscope,cathode luminescence,X-ray diffraction,reflection of vitrinite measurement,measurement of fluid inclusions,etc.Results Diagenesis includes compaction,cementation,dissolution and alteration.Cements are dominated by silicon,carbonate and clay minerals(chlorite,kaolinite,illite,illite/montmorillonite,and endellite).Diagenesis reaches A-period of middle diagenetic stage.Conclusion Diagenesis has control of succession of pore in sandstone reservoirs in the region of interest.Primary porosity loses severely under compaction and cementation in early diagenetic stage.Porosity of sandstone reservoirs is improved by dissolution of feldspar.But it came down again caused by ferroan calcite cementation.Losing of a great deal of primary porosity and underdeveloped secondary porosity are the main reasons of low porosity and low permeability of sandstone reservoirs in Jiyuan Oilfield,Ordos Basin.