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A B S T R A C TThe low-frequency theory of the White model to predict the dispersion and intrinsic attenuation in a single porous skeleton saturated with periodic layers of two immiscible fluids is extended to the full frequency range using the Biot theory. The extension is similar to the Dutta-Odé model for spherical inhomogeneities. Below the layer resonance frequency, the acoustic bulk properties for several gas-water fractions are in good agreement with the original White model. Deviations start to occur at higher frequencies due to the growing importance of resonance phenomena that were neglected in the original White model. The full model predicts significantly higher damping at sonic frequencies than the original White model. We also show that attenuation is significantly dependent on porosity variations. With realistic rock and fluid properties, a maximum attenuation of about 0.3 is found at seismic frequencies.

The location and extent of damage in a pipe can be remotely determined from weld and internal damage reflections using a single acoustic emitter/sensor pair. The use of normalised reflections yields single numbers enabling long distance data collection techniques such as wireless hopping. The attenuation is twice as high for opposite inner and outer fluids (whether air and water, or water and air) as compared to identical inner and outer fluids. The absolute recorded signals in the water-filled pipe are attenuated by a factor two compared to the empty pipe. The axial length of detection is reduced by a half. The reduction of >90% in sensors and the longer axial detection (>10× current state-of-theart-technology) means that permanent fixed sensor pairs for whole pipelines are on the horizon of possibility. The greatest advantage is envisioned in submersed pipelines.