The Rayleigh mode at the plane boundary between a liquid and a double porosity medium.

The Rayleigh mode (also called generalized Rayleigh wave) at the flat interface between a liquid and a double porosity medium saturated by the same liquid, is investigated. The double porosity medium obeys the phenomenological model of Berryman and Wang (2000). It allows the simultaneous propagation of three longitudinal waves and a transverse wave. Assuming open pore conditions at the interface, formulas are found for the coefficients of reflection in the liquid and of transmission in the double porosity medium. Considering only the angular variable in the study, numerical simulations based on data for Berea sandstone show the influence of frequency and the two types of porosity on the reflection coefficient and on the velocity of the generalized Rayleigh wave.

Effects of clogging on ultrasonic transmission through saturated granular single and double porosity media.

The clogging caused by the deposition of suspended particles modifies in depth several mechanical parameters (permeability, porosity, bulk moduli, etc.) of porous media and influences the acoustic behaviour. Consequently, at a fixed position in the medium, changes in phase velocity and attenuation are observed in the amplitude of the temporal signal of the transmitted waves. In this work, ultrasonic techniques are presented both for detecting and measuring the clogging in a water saturated porous medium. The acoustic measurements from the clogged samples are compared with the deposition profiles obtained at the end of injection experiments. Moreover, links are established between on the one hand phase velocity and the total porosity, and on the other hand the transmitted signal energy and the variation of porosity as consequence of particle deposition.

Ultrasonic characterisation of particle retention by a double porosity medium.

A study was undertaken to characterise the evolution of the clogging of various porous media during filtration experiments. Long-term tracer tests were carried out at various flow velocities. To highlight the effects of intraporosity on transport and retention mechanisms, both single porosity and double porosity media (DPM) were used. The presence of matrix porosity in the two investigated DPM provided additional sites, promoting retention of suspended particles (SP). The particle size distribution (PSD) of the recovered particles increased with time. However, and due to the additional retention sites in intraporosity, the changes in PSD with time were slower for tests on DPM. Ultrasonic transmission was used to detect modifications to the properties of the porous media induced by particle retention. The results demonstrate the capacity of ultrasound for detecting the evolution of physical clogging as a consequence of particle deposition.