Method for calculating water saturation of low-permeability reservoir

The invention discloses a method for calculating water saturation of a low-permeability reservoir. The method comprises the following steps of acquiring shale and formation water resistivity, parameters for reflecting a rock reservoir structure and connectivity, saturated rock conductivity, connected pore porosity, total porosity and shale content; calculating the volume ratio of the movable formation water to the fixed formation water in the reservoir; and calculating the water saturation of the reservoir according to the obtained parameters. According to the method, the saturated rock model of the low-permeability reservoir is established based on the effective medium conduction theory, the relation between the resistivity of the saturated rock and the water saturation is deduced, and the prediction precision of the water saturation of the low-permeability reservoir is effectively improved; and the method can be applied to low-permeability reservoir oil and water layer identification, and has important sign