The characteristics ofsedimentary facies and reservoir of the Chang 81 member in Pengyang-Jingchuan Area,Ordos Basin

Using the sedimentary structures and paleo-biotic features obtained from the drilling core to analyze the characteristics of sedimentary facies and reservoir of Chang 81 member in study area;using nuclear magnetic resonance,high pressure Hg injection,scan electron microscope,casting lamella and other methods to analyze the characteristics of chang 81 reservoir.The investigation finds the chang 81 member of the Pengyang-Jingchuan Area mainly developed the braided river delta frontal subfacies,and the delta plain facies only developed in the southwest of study area,and the four underwater distributary channels are almost distributed from NE to SW,the channel sand dominated the advantage space.The Chang 81 member sandstone are mainly gray,green-grayish lithic feldspathic sandstone and feldspar lithic sandstone,the intergranular pore and dissolved hole are main pore space of Chang 81 reservoir,and the pore type are mainly meso-and macroporosities,intergranular pore throat types are mainly micro throat and micro fine throa pore throat.The reservoir rocks are now in stage A of late diagenesis.Due to the compaction and presolution,cementation,the decrease of the primary sandstone porosity of each diagenesis are 23.8%and 27.35%;because of dissolution,the rate of face porosity slightly increased is 1.23%.After the research,it is believed that deposition and diagenesis are the main factors influencing physical properties in study area.