Characteristic of the shale gas reservoirs and evaluation of sweet spotin Wufeng-Longmaxi Formation:A case from the A well in Zhaotong shale gas demonsration zone

The shale in Wufeng Formation and 1th member of the Longmaxi Formation of the Well A in Zhaotong shale gas demonstration zone is taken as the research object in this study. Using thin section,scanning electron microscope, field emission electron microscope,nuclear magnetic resonance,liquid nitrogen adsorption,X-ray diffraction,geochemi- cal analysis and other testing methods,based on the petrology,organic geochemical and mineral composition,physical properties,pore types and structurmember of the Longmaxi Formation were evaluated,and the longitudinal shale gas sweet spot of the geological and en- gineering was optimized. The results show that the Wufeng-1th member of the Longmaxi Formation is mainly composed of siliceous shale,and the shale was mainly formed in the early transgressive period-regressive deep-water shelf facies poor oxygen-anaerobic environment. Bore organic matter and clay minerals content interlayer intragranular were mostly developed. Wufeng-1th member of the Longmaxi Formation reservoir porosity is mainly composed of medium holes, while microporous accounts for the largest contribution to the surface,and the medium holes and microporous provides the main pore volume. Long11 -Long21 sublayer relative to other sublayers has a relatively high TOC,porosity and gas content,and the indicators with upward trend to minimize or reduce. At the same time,the Long11 -Long21 sublayers have the rock mechanics characteristics of high brittleness index,low young’ s modulus and Poisson’ s ratio. Based on the geological and engineering comprehensive evaluation,the Long11 -Long21 sublayers namely carbon-rich high silicon shale section is a sweet spot in vertical section,and it’ s also the horizontal well target segments in the Zhaotong shale gas demonstration zone.e characteristics and hydrocarbon content,the reservoir characteristics of Wufeng-1th