A squirt-flow theory to model wave anelasticity in rocks containing compliant microfractures.

Wave propagation in rocks induces fluid pressure gradients and flow between stiff intergranular pores and compliant microfractures. This, in turn, leads to wave anelasticity, i.e., attenuation and velocity dispersion. Three known squirt-flow models attempt to explain this phenomenon. Based on these theories, we reformulate a new one, where we derive the dry-rock moduli on the assumption that the boundary fluid pressure is constant. The new model improves the predictions of the other models, e.g., a better description at high frequencies and the inclusion of permeability effects. The numerical example shows the response due to the characteristic squirt-flow length and fluid viscosity on wave propagation. The reformulated model is applied to experiments made on water-saturated tight sandstones, where the squirt-flow length is determined, showing that it increases with increasing permeability and porosity at full saturation. • A new squirt-flow model by deriving the dry-rock moduli on the assumption of the constant boundary fluid pressure. [ABSTRACT FROM AUTHOR]