Sandstone diagenesis of Chang 4+5 reservoir in Ganguyi Oilfield of Ordos Basin

Based on the analysis of casting lamella,scan electron microscope and X-ray diffractions,a study was carried out on the characteristics of petrology and diagenesis of Chang 4+5 reservoir in Ganguyi Oilfield,Ordos Basin.The result shows that the main sandstone in the area is arkose with low compositional maturity.The diagenetic characteristics of Chang 4+5 sandstone show that this set of sandstones are in the early A period of the late diagenetic stage at present.The early diagenetic compaction and multi-mineral cementation are major effective factors that lead to the poor astrophysical property of Chang 4+5 reservoir, while dissolution,in particular dissolution of feldspar,is one of significant factors controlling the quality of the reservoir.