Feasibility study on shale gas reservoir fracturing in the upper member of the Second Member of Kongdian Formation in the Weibei sag

The upper shale in the Second Member of the Eocene Kongdian Formation is a good shale gas reservoir in the Weibei Sag, Jiyang Depression. In order to understand the feasibility of shale gas reservoir fracturing in the upper member of the Second Member of the Kongdian Formation, based on core observation, organic geochemical analysis, logging, scanning electron microscopy analysis, X-ray diffraction, rock mechanics test analysis, this article studied the lithologic characteristics and organic ground of the upper section of the second section, geostress characteristics, fracture development characteristics, mineral content characteristics, rock mechanics characteristics, brittleness index, etc. of the Kongdian Formation chemical characteristics.The results show that the thickness of the shale in the upper member of the Second Member of the Kongdian Formation in the Weibei Sag is 40~160 m, the mud-to-earth ratio is greater than 70%, the organic carbon content is generally 1% to 3%, and the vitrinite reflectance is 0.78%~1.04%; the type of kerogen is mainly type II1, and the average desorption gas content on site is 1.2 m3/t; the maximum horizontal principal stress direction is near east-west direction; the crack develops in mudstone, the micro-crack extends along the mineral gap, and connectivity is good; brittle mineral content is 43.4%~65.2%, rock brittleness index calculated from brittle minerals is 42.5%~64.7%, brittleness is strong, clay mineral content is 34.8%~56.6%, and water sensitive montmorillonite is seldom; rock brittleness index obtained by rock mechanics calculation is about 6%, showing poor brittleness. In summary, the shale gas reservoir in the upper member of the second section of Kongdian Formation in the Weibei Sag has good compressibility, and is beneficial to fracture transformation, but there are also certain risks. © 2019, Science Press. All right reserved.