Stress sensitivity of elastic moduli and electrical resistivity in porous rocks

Stress dependences of elastic moduli and velocities for anisotropic rocks and electrical resistivity are derived as functions of pore space deformation due to an applied arbitrary load. All dependences have the form of a four-parametric exponential equation V(P) = A + KP - B exp(-DP). The stress dependences are mainly controlled by the tensor of stress sensitivity. One result of our derivations is that if this tensor is isotropic and the rock sample is loaded hydrostatically, the argument D of the exponential term is a universal quantity for all mentioned rock characteristics. We show that laboratory-derived velocity, dilatancy and resistivity measurements as a function of effective pressure support this result.