Squirt flow influence on sonic log parameters

Abstract

Most sedimentary rocks contain movable fluid in the pores. Hydrodynamic effects due to wave-induced oscillatory fluid flow can lead to significant changes of velocities and attenuations of elastic waves in these rocks. In this paper, we consider the influence of a squirt flow (local flow between the pores of different compressibility) on the sonic log response. The calculations are performed using a unified model describing the joint influence of squirt flow and Biot's global flow. The results show that the influence of the squirt flow increases with increase of a signal frequency. This influence is relatively small in the case of the Stoneley wave but it is significant in the case of P and S waves.