Effects Of A Logging Tool On The Stoneley Wave Propagation In Elastic And Porous Formations

Abstract

A detailed study is carried out to investigate the effects of an acoustic logging tool on the propagation characteristics of Stoneley waves in both elastic and porous formations. In an elastic formation, the presence of the tool in the borehole reduces the Stoneley velocity and enhances the Stoneley wave excitation. When intrinsic attenuation due to formation and bore fluid anelasticity is present, the tool reduces Stoneley attenuation due to fluid and increases the attenuation due to formation. For a permeable porous formation, the simplified Biot-Rosenbaum model of Tang et al. (1990) is modified to incorporate the effects of the tool on the Stoneley propagation. The presence of the tool increases the sensitivity of the Stoneley waves to the formation flow properties. Specifically, the dispersion of Stoneley velocity due to formation permeability is increased and the attenuation of the Stoneley waves is more pronounced, compared with the results without the tool. Consequently, in the determination of formation flow properties using Stoneley wave measurements, the effects of permeability may be better estimated using a tool with large diameter.