Abstract:
The stable shale gas flow was obtained during vertical well drilling of Qianshuidi 1 Well in Guizhong-Nanpanjiang area, meaning the good marine shale gas was discovered in Carboniferous Dawuba Formation. Based on the drilling, logging, well logging, analysis and testing data, the authors in this paper comprehensively studied the lithofacies, organic geochemistry, physical properties, fracture development and gas bearing of Dawuba Formation shale reservoir, and explained the gas bearing and compressibility of shale reservoir in the study area. The results show that: ① Dawuba Formation consists of a set of huge thick shale system which is from the lower slope subfacies of carbonate slope facies to the huge thick shale series of platform basin facies, and Good to high-quality source rock are well developed in the middle lower part of the third member and the upper part of the first member, with developed natural fractures. The maximum value of total hydrocarbon in gas logging is 63.41%, and the average value of desorption gas is 1.08 m
3/t, with good shale gas generation conditions and resource potential. ② The total content of brittle minerals in the main gas bearing intervals is 31%~94%, and the average Poisson's ratio is 0.31. The average bulk modulus of elasticity is 27.2 GPa, and the fracture pressure is between 29.7 MPa and 48.5 MPa. This set of strata has good fracture potential and fracture retention ability, which means the complex fracture networks would be easily formed under large-scale volumetric fracture. Besides, the set of strata has high pressure and meets the conditions for fracturing to form industrial production capacity, making it a target layer for further exploration and development.