Reply to Comment by Y. Kovalyshen on “Ultrasonic Monitoring of Spontaneous Imbibition Experiments: Precursory Moisture Diffusion Effects Ahead of Water Front”

Abstract

We tested on a data set including 12 different rocks the assumption that, during water imbibition experiments, the interaction between direct P waves and reflected P waves on the imbibition front could explain the early P wave amplitude variation occurring before any velocity variation. Our calculations show that (i) the observed distance between the water front and the ultrasonic sensors is always larger than the estimated critical distance below which the first peak amplitude is impacted by the reflected P wave, (ii) the magnitude of the coefficients of reflection is generally very small, and (iii) using simulations of composite waveforms, an impact on the first peak amplitude is expected only in 25% of the tested samples. P wave interaction is definitively a mechanism which can lead to amplitude variations, but it is very likely that such a mechanism is not responsible for the early amplitude variation detected in most of the tested rocks. Moisture diffusion is still a very relevant mechanism to account for our observations on P wave amplitude variations during capillary rise.