Diagenesis of Chang6 Reservoir in Xuecha Block of Wuqi Area

In order to evaluate and forecast the Chang6 reservoir of low porosity and super-low permeability sandstone in Xuecha block of Wuqi area in Ordos basin,describe the reservoir subtly and develop it effectively,this paper studies the reservoir diagenetic mechanism and reveals the diagenesis-physical property evolutionary law based on the data analysis of casting lamella,scan electron microscope,X-ray diffraction,electron probe,oxygen and carbon stable isotope and vitrinite reflectance.The results show that the Chang6 reservoir is now in the late diagenetic phase A to B;main diagenesis include compaction,cementation,metasomatosis,cataclasis and hydrocarbon emplacement;the intense compaction is the radical contributor to the pore beravement in early phase and the ferroan calcite cementation in the late diagenetic phase induces the severe heterogeneity of physical property;dissolution,grain-coating chlorite,cataclasis and hydrocarbon emplacement work on physical property constructively;pore types of Chang6 reservoir mainly include primary remained intergranular pore,feldspar dissolved pore and lithic dissolved pore,secondly micropore and fracture pore;the reservoir is characterized by fine throat,worse sorting,worse connectivity;the heterogeneity of the micro-pore structure is intense.Meanwhile,reservoir diagenetic evolutionary sequence and the history of porosity evolution are analysed.