MEASUREMENTS OF ACOUSTIC SURFACE-WAVES ON FLUID-FILLED POROUS ROCKS

Novel experimental techniques to measure ultrasonic velocity and atten uation of surface waves on fluid-filled porous natural rocks are prese nted. Our experimental results are consistent with the theoretical pre dictions of Feng and Johnson (1983). Depending on the interface condit ions, i.e., whether the surface pores are open or closed, pseudo-Rayle igh, pseudo-Stoneley, and/or true Stoneley surface waves may exist on fluid-saturated rocks. We have demonstrated the existence of the ''slo w'' surface wave (true Stoneley mode) on fluid-filled porous rocks wit h closed surface pores. The velocity and attenuation of the ''slow'' s urface mode may be used to assess the dynamic permeability of porous f ormations.