Abstract:From the analysis of cores observation, thin sections, casting thin sections, scanning electron microscopy (sem) and mercury intrusion datas of Chang 8 formation in west of Mahuangshan area,Ordos Basin,focusing on the diagenesis, pore and permeability conditions, recognize and classify diagenetic facies based on core Wells, optimizing choose GR, AC, DEN, ILD, ILM and CNL logging curve to establish the well logging identification standards of diagenetic facies, to forecast the diagenetic facies distribution. The reservoir of Chang 8 formation in studied area recognized porphyritic corroded porosity diagenetic facies, carbonate cemented tight diagenetic facies, clay minerals cemented tight diagenetic facies and compacted tight diagenetic facies. The porphyritic corroded porosity diagenetic facies mainly developed in underwater distributary channel microfacies, have best property, the best transverse ductility and connectivity. Carbonate cemented tight diagenetic facies and clay minerals cemented tight diagenetic facies mainly developed in underwater distributary channel, sheet sand, debouch bar microfacies, have better porosity. Compacted tight diagenetic facies mainly developed in distributary bay microfacies and predelta mud microfacies, with the worst porosity, continuous development, which is the best developed diagenetic facies type in studied area. High quality diagenetic facies mainly developed in advantage sedimentary microfacies, diagenetic facies have controlling function to permeability. Porphyritic corroded porosity diagenetic facies have the highest testing oil nissan and unit productivity, which means high quality diagenetic facies type mainly developed in high quality reservoir, high quality diagenetic facies is good for oil and gas enrichment.