Abstract:

In order to study the shale gas exploration potential of Upper Paleozoic in Ordos basin, organic-rich shale samples of Shanxi Formation are selected to test the organic geochemistry, physical properties and isothermal adsorption, etc. then the parameters are dealt with mathematical statistics methods and the corresponding logging characteristics are analyzed. Effective shale thickness changes greatly and it can reach more than 15 meters, the main part of TOC content is more than 1%, organic matter types are mainly type Ⅱ₂ and type III, vitrinite reflectance is 1.66% on the average and it belongs to mature-high mature stage which is good for the formation of pyrolysis gas. The Shanxi Formation has the essential conditions to form shale gas reservoir. Clay minerals are mainly composed of 44.9% illite and 33.6% kaolinite, shale porosity is 3.98% and permeability is 0.133×10^-3 μm² on the average, shale adsorption content is 1.94 m³/t. Considering the effective thickness of mud shale, organic matter content and type, degree of thermal evolution, gas content and other factors, the favorable shale gas areas  of Shanxi Formation are mainly located in the northwest corner of Tianhuan depression, the north-east corner of north Shaanxi slope and the central-southern part of Ordos basin.

Key words: shale gas, clay minerals, exploration potential, Shanxi Formation, Ordos basin