Borehole modes in a cylindrical fluid-saturated permeable medium

Abstract

Utilizing the borehole Stoneley wave generated in a permeable sample is a promising technique for measuring the frequency-dependent nature of permeability. The cylindrical boundary of the sample introduces complex extensional modes. In this article, numerical results of modes associated with an axially symmetric fluid-filled borehole in a cylinder of permeable medium are presented. Besides the Stoneley mode, there are two classes of extensional modes: the fast-wave modes and the slow-wave modes. These modes vary as functions of the sample permeability and size. In a highly permeable sample, the slow extensional modes, having velocity and attenuation near the Stoneley mode at low frequency, can obscure the identification of the Stoneley mode.