About Permeability Evaluation by Acoustic-magnetic Logging

New way for permeability evaluation of fluid-filled rock surrounding an uncased borehole based on electrokinetic effect is suggested. This approach is based on Pride’s model describing the coupled propagation of acoustic and electromagnetic disturbances in porous elastic media saturated by an electrolyte. Arising acoustic and electromagnetic waves excited by an acoustic emitter. On the basis of numerical modeling it is established, that the ratio of complex-valued amplitude of Stoneley wave of azimuth component of magnetic field to complex-valued amplitude of Stoneley wave of pressure is very sensitive to variation of formation permeability and mudcake stiffness. These amplitudes are determined from expansions of registered wave trains of pressure and azimuthal component of magnetic field in terms of plain waves. For open and sealed pores on borehole wall the approximate analytical expressions for this ratio are presented. For these cases by fit of appropriate parameters of these expressions it’s possible to evaluate rock permeability.