Effect on ultrasonic signals of viscous pore fluids in unconsolidated sand

Abstract

Ultrasonic attenuation measurements in unconsolidated sand with pore fluids ranging in viscosity between 0.001 and 1 Pa•s were compared with the predictions of fluid flow and scattering theories. Laboratory experiments were performed for P waves propagating through sand samples saturated with water, castor oil and two different silicone oils. The attenuation shows a frequency squared dependence for all measurements, regardless of viscosity, in the range between 100 and 1000 kHz. The results show that for unconsolidated sand, fluid flow models which imply significant effects of the viscous pore fluids on ultrasonic waves cannot explain the laboratory measurements. The main attenuation effects observed in the laboratory can be simulated with a three-dimensional generalized dynamic composite elastic medium model, which includes scattering from the pores and grains as well as intrinsic attenuation caused by the viscous pore fluids. For the studied sand samples, scattering is the main attenuation mechanism for ultrasonic P waves.

Experimental Study of Sound Waves in Sandy Sediment

“…(4-37). This agrees with an experiment previously referenced, [33], which concluded "attenuation shows no correlation with the viscosity" of the fluid in unconsolidated sand. Note that up to now all graphed parameters are measured.…”

“…Seifert et al, [33] did an experiment with sand saturated with fluids of different viscosities (water, two different silicon oils, and castor oil) to measure attenuation. They stated, "Biot's theory shows that acoustic waves create relative motion between the fluid and the solid matrix due to inertial effects, resulting in viscous dissipation of acoustic energy."…”

Frequency Dependence of Phase Speed, Group Speed, and Attenuation in Water-Saturated Sand: Laboratory Experiments

“…The attenuation in the sediment was then determined as a function of the frequency from the ratio between the magnitude of the Fourier transforms obtained in the case of sediment and water. It was [18] and Lee et al [19]. (The stars correspond to the scattering attenuation obtained by Seifert and the circles to data by Lee et al) again assumed that there was no attenuation in fresh water (the reference medium).…”

A survey of the geophysical properties of chlorinated DNAPLs

“…Acoustic n-dodecane 90 kHz Seifert (1998) Acoustic Silicone oil 900 kHz Castor oil n-dodecane Seifert et al (1999) Acoustic Silicone oil 900 kHz Persson and Berndtsson (2002) Dielectric SFSO 10 MHz-800 MHz Francisca and Rinaldi (2003) Dielectric Paraffin 20 MHz- 1.3 GHz Lubricant oil Geller et al (2003) Acoustic TCE 500 kHz Toluene Ajo-Franklin et al…”

“…Reductions in Vp of up to 40.3% were observed for sands fully saturated with freon-113. Seifert (1998) and Seifert et al (1999) performed a similar set of measurements with a focus on varying fluid viscosity and wetting properties. P-wave velocity and attenuation were measured while saturating with two different grades of silicone oil (10 and 100 cs), castor oil, and n-dodecane.…”