Investigation of Acoustic Emission Caused by Filtration of an Air Flow through a Porous Medium
- 1 Department of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Nizhny Novgorod, Russia
- 2 Department of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Nizhny Novgorod, Russia
Abstract
We study characteristics of acoustic emission caused by an air flow filtered through samples of solid porous pumice either partially filled with glycerin or dry. Some peculiarities of the laboratory setup and the performed experiments are described. Samples of different porosity and several values of the air pressure drop are tested. Physical reasons for the difference in acoustical emission spectra of samples of different porosity and in the relaxation times of the acoustic emission level caused by different porosity and fluid saturation are discussed. It is proposed to use the phenomenon of acoustic emission for detecting the fluid trapped in the pores of cores. The existing results based on the borehole field experiments are rough. The frequency range of signals recorded in these experiments is less than 5 kHz (up to 10 kHz). It is shown by our laboratory measurements that the required frequency band should be up to 50 - 60 kHz to reflect the features of the spectral composition of the acoustic emission in predicting the fluid content. The level of acoustic noise under field conditions is much higher, i.e., by 10 - 15 dB, than the noise achieved under laboratory conditions. Since the sensitivity of the recorders and the frequency range are considerably higher in our experiments, they are unique when applied to the solved problem.
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