Heterogeneity characteristics and controlling factors of black shale in Jiaoshiba, Fuling, Sichuan Basin

The study of macroscopic and microscopic heterogeneity of shale is one of the core aspects of shale gas exploration and development. The black shale in Jiaoshiba area in Fuling of Sichuan Province can be divided into two third-level sequences and nine sub-layers. The macroscopic heterogeneity mainly shows as follows. Laminations decrease first and then increase from bottom to top, sandy bands first increase and then decrease, while pyrites gradually decrease. Graptolithina in the transgressive system tract is mainly diplograptus type, while those in the early and late high system tracts are mainly monograptus type. Graptolithina abundance gradually reduces from bottom to top. The microscopic heterogeneity mainly shows as follows. TOC content in the transgressive system tract is the highest, and then decreases upwards, while clay mineral content gradually increases from bottom to top. On the whole, three kinds of sedimentation, bio-current, isochronous flow and terrigenous source, jointly controlled the heterogeneity of black shale in the Jiaoshiba area.