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Anelasticity of porous rocks containing microcracks: a reformulation of the BISQ model

C. Wu, J. Ba, L. Zhang and J.M. Carcione

Abstract: 

The BISQ model unified the Biot theory and the squirt-flow mechanism. The squirt flow is induced by the compression of the pore volume due to the wave excitation and pressure gradients between stiff pores and microcracks. On the basis of this model, we consider the fluid in microcracks to oscillate perpendicular to the wave direction, which is independent of the global (Biot) wave oscillation. The BISQ theory is, then, reformulated in terms of the law of conservation of fluid mass and the crack aspect ratio and density, hereafter called Re-BISQ model. The BISQ model is a particular case of the Re-BISQ model if the microcrack porosity to total porosity ratio is set to one. We analyse the effects of rock properties, such as the permeability and the characteristic squirt length. Comparisons with ultrasonic experimental data indicate that the Re-BISQ model provides a better description of the wave properties than the original BISQ model.