Method for establishing unsteady seepage model of shale gas reservoir

The invention discloses a method for establishing an unsteady seepage model of a shale gas reservoir, which comprises the following steps: S1, proposing assumed conditions on the basis of a Gilman-Kazemi model that adsorption-state and free-state gases exist in a matrix system at the same time, and the temperature of the shale gas reservoir is kept constant, the compressibility of reservoir rock is ignored; S2, establishing an unstable seepage differential equation, including establishing a shale gas state equation, a motion equation and a continuity equation; S3, analyzing apparent matrix permeability and apparent fracture permeability of the shale gas reservoir; and S4, establishing a shale gas reservoir double-medium unstable seepage model: firstly establishing a matrix unstable seepagedifferential equation and a crack unstable seepage differential equation, and then establishing a system comprehensive seepage differential equation based on the matrix and crack unstable seepage differential equation. Accor