A Nonlinear Relaxation Mechanism of the Filtering Noise Generation in Porous Media

We propose a model that explains the microscopic origin of the nonstationarity and related filtering noise generation in porous media. The noise is not determined by hydrodynamic sources, and the transition to a turbulent flow regime in pores is not required for its occurrence. The physical mechanism of a nonstationary flow is connected with the development of instability at contacts inside cracks or grains, as well as with the presence of relaxation phenomena in voids and channels always available in rocks. It has been shown that the structural elements in rocks provide a self-excited oscillation regime. The proposed model is in good agreement with known experimental data.