Diagenesis of Chang 6 reservoir of Xiasiwan area in Ordos Basin

In order to reveal the spatial evolution rule of diagenesis and porosity evolution,the characteristics and diagenesis stage of the Chang 6 reservoir are studied based on the data analysis of rock section,casting thin-section,scan electron microscope,X-ray diffraction and vitrinite reflection of Xiasiwan area in Ordos Basin.The results show that the Chang 6 reservoir is in the late diagenesis phase A;and main diageneses include compaction,cementation,metasomatosis and cataclasis.The intense compaction is the primary cause leading to pore loss of the reservoir in early period;the cementation of ferrocalcite in late diagenetic stage is the main factor leading to the severe heterogeneity of reservoir physical property;dissolution,grain-coating chlorite,and cataclasis have constructive effect on the reservoir physical property.The pore types of the Chang 6 reservoir mainly include primary remained intergranular pore,feldspar dissolved pore and lithic dissolved pore,secondly micropore and fracture pore.Finally,reservoir diagenetic evolutionary sequence and the history of reservoir pore evolution are analyzed.