Reservoir Characteristics And Logging Interpretation Of Carbonate In The Upper Majiagou 5th Formation In Southern Zhidan,northern Shaanxi

The study area of this paper is Southern Zhidan, located in Shanbei slope of Ordos basin, and the study section is member from ?6 of Majiagou Formation. In order to figure out its lithologic and physical characteristic,pore types,structure feature.and main diagenesis, this paper adopts many research methods and means, such as core description, thin section identification,porosity and permeability analysis.mercury analysis, and carbon and oxygen isotope analysis.The study result shows that the main rock types of member 54?5】include dolomicrite, corrosion carneule, dolarenaceous. dolorudite, sparry oolitic dolomite.while the main rock type in member 6 is micritic limestone.Reservoir properties is poor with a special low porosity and low permeability.The reservoir space of carbonate rocks is mainly secondary pore, including intercrystalline pore?intercrystalline solution pore, gypsum mould hole, salt mould hole and crack.Diagenesis is complex and diverse, including dolomitization. dissolution, compaction-pressure solution?recrystallizatioru cementation and packing action.In this paper, the density- neutron method is used to identify the intersection of carbonate rocks and to determine the matrix porosity reservoir, while crack identification method is used to interpret and determine the types of cracks and crack porosity.At last this paper clears the rules and characteristics of reservoir distribution,The reservoir is mainly distributed in M5]2?M5!3?M52% and M541 layer, the other layers of reservoir are of poor development, small thickness and patchy distribution-spread along the northwest- southeast direction. The average reservoir thickness is 4 metre, mainly classified into Type III Reservoir.