Fracturing subsection optimization method for shale gas horizontal well

The invention relates to a fracturing subsection optimization method for a shale gas horizontal well. The method comprises the following steps: an isochronous stratum framework of shale is established; under the isochronous stratum framework, shale under the isochronous stratum framework is differentiated into various shale facies on the basis of element logging data; lithology and the like of theshale facies are determined based on the logging response characteristics; a vertical sequence of shale is established according to lithology and the like of the shale facies and a vertical contact relation of a stratum, wherein the vertical sequence comprises a target layer, an upper cladding layer and a lower cladding layer; during horizontal drilling of the target layer, logging while drillingand element logging are carried out, and geological guidance is carried out according to the logging while drilling and element logging, so that a horizontal section is drilled in the target layer; the shale facies of the hor