Applicability Analysis of the Fluid Term in the Gassmann Equation for the Tight Sandstone Reservoir

The petrophysical properties of the tight sandstone reservoir are different from those of the conventional sand-shale reservoir, which are characterized by low porosity, low permeability, and complex pore structure. It brings troubles for fluid identification of the tight sandstone reservoir. Based on the new partial-connected-pore rock physics model, the elastic moduli are analyzed. When the pores are all connected or the aspect ratio of pores is 1, the fluid term of the Gassmann equation is strictly applicable for tight sandstone reservoir. However, with the increase of soft-pore-porosity and the decrease of connected-pore-porosity, the description of the fluid characteristics by using the fluid term of the Gassmann equation becomes worse.