Diagenesis study of the chang 2 and chang 1 reservoirs of the upper triassic in the jiyuan oilfield

Based on analysis of common rock slice,casting lamella and scanning electron microscope data,this paper further studies the diagenesis of this area.Diagenetic stage is determined of the Chang 2 and Chang 1 reservoirs in the Jiyuan oilfield,A diagenetic evolution model is established and the effect of the main diagenesis on reservoir quality is studied.The result shows that the diagenesis in this area mainly includes compaction、Carbonate cementation、Chlorite cementation、Kaolinite cementation、quartz secondary、volcanics denudation、feldspar and debris particles denudation.Diagenesis of this reservoir reaches A-period of late diagenetic stage,secondary dissolution pore is the main pore form. Digenesis has control of succession of controlling to sandstone reservoirs in the region. Because the size of sand particle in this study areas is smaller and low compositional maturity,this area has a strong compaction.This is the most important factor to result in reduced porosity.Volcanic material and debris particles of feldspar dissolution are the key to porosity development.At the same time,such as the late calcite,rail calcite of carbonate cement made sandstone porosity reduced once again.