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The advent of new high resolution seismic reflection and borehole sonic techniques has stimulated renewed interest in what information stress wave propagation may carry about rock properties and pore fluids in situ.We have measured extensional and shear wave velocities. I• e and I•,, and their specific attenuation, Q•-i and Q•-i, in Massilon sandstone and Vycor porous glass as a function of continuously varying partial water saturation and relative humidity. Measurements were made at frequencies from 300 Hz to 14 kHz using a resonant bar technique and from 25-400 Hz using a torsional pendulum technique. Energy loss is very sensitive to partial water saturation. In Massilon sandstone, Q•-i is maximum and greater than Q;-1 only at full saturation. Q•-i rises to a strong peak at 85% water saturation. Energy loss drops significantly as the Massilon becomes "very dry." Q•-i and Q•-i in partially saturated Massilon and Vycor are strongly frequency dependent throughout the acoustic range, exhibiting peaks between 1-10 kHz. Q-1 in dry Massilon and Vycor is independent of frequency, at least in the acoustic range. Two pore fluid mechanisms absorb energy. Viscous dissipation due to fluid flow in pores dominates in fully and partially water saturated materials. A surface capillary film mechanism dominates at low moisture contents. Nonlinear frame mechanisms such as frictional grain sliding are not signficant at normal acoustic strains, even in "dry" rocks. Compressional wave velocity and specific attenuation, l•p and Q•-i, and bulk compressional specific attenuation, Q;-1, were calculated at given frequencies. While the dependence of velocities on water saturation agrees well with a very simple explanation, there is no satisfactory theory yet available for attenuation. Vp/V, and Q;1/Qs-1 provide sufficient information to distinguish between fully and partially water saturated Massilon sandstones, yet are insufficient to resolve the degree of partial water saturation. PACS numbers: 43.35.Cg, 91.60. --x, 43.40.Ph INTRODUCTION Specific attenuation, Qq, is a dimensiontess measure of the energy loss per cycle as a stress wave propagates through a dissipative material. It is preferably defined as 1/Q =/l•/4rrW, (1) where ß is the energy toss per cycle and W is the, average energy stored per cycle. gccurate estimates of Q-t in sands and sandstones are necessary in order to reliably predict the path and decay of tow-frequency sound which travels through the ocean floor. 2'• In geophysical exploration, an understanding of how acoustic energy toss depends on pore structure and water saturation may advance the interpretation of borehole sonic togs and high resolution seismic reflections. 7 Consider that much of the original technical motivation for the analysis of"bright spots," observed in seismic reflections, arose from a limited understanding ultrasonic velocities as a function of partial water saturation. TM Despite the pioneering results of Biot, t3'l* Winkler, •s'19 and others, 2ø'23 I think it safe to say that in geophysics as ...

Partial fluid saturation affects absorption and dispersion in sandstones. The proposed theoretical model describes acoustic relaxation due to local fluid flow. Previously proposed models of local flow were based on microgeometries not representative of sedimentary rocks; they were unable to describe the behavior of partially saturated sandstones. The new model is based upon observed microstructures in sandstones. A fraction of the grain contacts in sandstones are permeated by sheet‐like gaps. The incomplete solid‐solid contact allows an interconnected fluid film to exist between the grain surfaces. The model consists of a narrow gap connected to a finite annular pore. An acoustic stress wave drives the film out of the narrow contact region and into the adjacent pore. The viscous flow results in a dissipation of energy. The model predicts the real and imaginary parts of the complex frame moduli as a function of frequency and fluid saturation. The predictions agree well with experimental results.

This paper describes the observation and computer simulation of the rotational Raman spectrum of water vapor and the measurement of the depolarization ratio for Rayleigh scattering from water vapor, which was found to be (3.0±1.4) ×10−4. These results were combined with the value of the mean polarizability to calculate the principal polarizability components of the water molecule. At 514.5 nm, they are (in units of 10−24 cm3): αxx=1.468±0.003, αyy =1.415±0.013, and αzz=1.528±0.013, where the x axis is the dipole axis and the y axis is perpendicular to the molecular plane.

The acoustic properties of tight sandstones are very sensitive to partial gas/water saturation. Measurements at 5 kHz show that compressional velocity drops sharply with undersaturation. Extensional and shear losses at 5 kHz are large in both fully and partially saturated sands. The shear loss Qs−1 declines linearly with increasing gas content. The extensional loss Qe−1 peaks at 0.80 water saturation, Q−1 is frequency dependent. The attenuation is well explained by hydrodynamic relaxation in the grain contacts. The measurements indicate velocity dispersions consistent with this mechanism. Ultrasonic velocities at 500 kHz are roughly 10–25% higher than acoustic velocities at 5 kHz. The ultrasonic velocities exhibit a weak dependence on saturation. Frame moduli are unrelaxed at these frequencies.