川南五峰组—龙马溪组低阻页岩特征分析及启示OA北大核心CSTPCD

There are low resistivity anomalies of shale gas reservoirs of Wufeng-Longmaxi Formation in Changning and Luzhou areas in southern Sichuan Basin,and the gas production of low resistivity wells in different areas varies greatly.Based on the data of physical properties,geochemistry,X-ray diffraction,thin section,gas content,production test and logging curve,the characteristics,genetic factors and their effects on gas content of different types of low resistivity are studied.The results indicate that the boundary between low resistivity well and normal resistivity well in shale gas reservoir is 15 Ω·m,and the resistivity range of sub low resistivity well is mainly 10～100 Ω·m.The curve shape characteristics of low resistivity well mainly include"continuous decline type"(Rt＜5 Ω·m)and"first decrease and then increase type"(5～15 Ω·m).The origin factors of low resistivity mainly include graphitization caused by over mature organic matter,high water saturation,high pyrite content and high clay mineral content,which play a different role in the reduction of resistivity of different types;Low resistivity wells of"continuous decline"generally have poor gas content,but the"first decrease and then return to increase"generally have good gas content.The low resistivity shale at the bottom of the syncline structural belt and at a large buried depth is usually"continuous decline",and the gas-bearing properties and test productivity are usually very low.It is a type that needs special attention in the risk exploration and development of low resistivity shale gas.