A novel anisotropy template for an improved interpretation of elastic anisotropy data

Abstract

AbstractTight unconventional rocks are characterized by the presence of laminations, preferentially oriented cracks, and an interconnected network of compliant minerals. Such anisotropic features can mechanically deform due to pressure depletion during production, leading to a human-induced change of elastic and fluid transport properties. Rock physics models allow us to better predict and assess stress- and direction-dependent elastic moduli of the rock, useful for horizontal stress estimates. However, elastic anisotropy can be challenging to measure and interpret. We have developed an anisotropy template that can be used to assess stress-dependent changes in elastic moduli and investigate rock textures. We present here the template construction using an effective medium model consisting of stiff and compliant layers and crack inclusions and evaluate the origin of stress-dependent stiffness changes in acoustic data from Berea, Bakken, Three Forks, and Mancos formations.