Patent ID: 7676349

Claim:
A method for generating an anisotropic rock-physics model that relates elastic properties to petrophysical properties as a function of location in a subterranean region, wherein said model simulates both shale anisotropy and stress-induced anisotropy and has a pore volume, a shale volume and a sand volume, said method comprising: (a) dividing the model's pore volume into clay-related pores, sand-related pores, and microcracks, wherein the model's pore volume is divided according to estimated shale volume and effective stress; (b) selecting mathematical relationships whereby said division of the pore volume into three parts can be made quantitative based on estimates of overburden stress and shale volume fraction in the subterranean region; (c) mixing sand grains with clay particles in said model using a first mixing law; (d) adding wet clay pores with a preferred orientation distribution to the clay-related part of the pore volume of said model; (e) adding empty sand pores and aligned microcracks to the sand and microcrack parts, respectively, of the pore volume of said model; (f) mixing hydrocarbons with water using a second mixing law; thereby forming a fluid mixture within said model; (g) placing the fluid mixture into the sand pores and microcracks of said model using anisotropic Gassmann theory; (h) calibrating parameters in the model using measured data, wherein the calibration data include laboratory measurements or well logs; and (i) using the calibrated model to relate petrophysical properties and elastic properties in the subterranean region.