Planar and vertical heterogeneity of Wufeng-Longmaxi shale and their influence on “sweet spot”selection and reservoir stimulation were analyzed through comparison of geological parameters including mineral composition，physical properties，gas content and fracability，as well as their vertical varying regularities in Jiaoshiba，Changning and Weiyuan gas fields. The study shows that the vertical heterogeneity is consistent in different regions：Quartz content，TOC and gas content all present the trend of decreasing from bottom to top，and the bottom shale interval deposited in deep-water shelf environment is generally characterized with high TOC，high brittleness，high porosity and high gas content. The coupling and matching of a series of properties and parameters leads to the “sweet spot” mainly developed during Wufeng-Rhuddanian stage. Planar heterogeneity causes the regional variation of reservoir quality：The calcareous content in Changning and Weiyuan regions is obviously higher than that of Jiaoshiba region，and the calcareous-siliceous mixed shale is developed in the former region. Jiaoshiba region is featured with smaller horizontal stress difference and better-developed natural fracture comparing with Changning and Weiyuan regions，which are both more favorable for reservoir fracturing. The“sweet spot”in Changning and Jiaoshiba regions is mainly the interval of Wufeng-Lower Rhuddanian，while the“sweet spot” in Weiyuan region is mainly the interval of Rhuddanian-Middle Aeronian. Heterogeneity of shale reservoir controls the distribution scope，interval and thickness of “sweet spot”. And the spatial variation of mineral composition，natural fracture，rock mechanical parameters and in-situ stress are all the basis of hydraulic fracturing design.
Zhang Chenchen Dong Dazhong Wang Yuman Li Xinjing Shi Zhensheng Qiu Zhen Guan Quanzhong. Heterogeneity characteristics of Wufeng-Longmaxi shale reservoir in Sichuan Basin[J]. Chinese Journal of Geology, 2017, 52(1): 170-185.