Anisotropic Rock Physics Modeling for Tight Sandstone

One distinguishing feature of low-porosity and low-permeability sandstones is the departure of the behavior of their elastic properties from that of general porous and permeable sands. This paper put forward the method to integrate rock physics model in tight sandstones due to the properties of developed cracks and its effect on tight sand. It focused on the derivation of fluid substitution equations by combining Hudson theory for the dry cracked rock and Gassmann’s (1951) anisotropic fluid substitution equations. Then analysis was made to calculate the elastic modulus in tight sandstones with different crack properties. At last, this paper discussed the accuracy of the parameters estimation method based on rock physics model considering micro cracks, compared the estimated P-wave and S-wave velocity with the experimental measurement data and the log value, extracted Thomsen parameters of fracture reservoir, and analyzed the degree of anisotropy.