Ultrasonic wave propagation in dry and brine-saturated sandstones as a function of effective stress: Laboratory measurements and modeling

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Geophysical Prospecting

DOI:https://doi.org/10.1111/j.1365-2478.1995.tb00255.x· OSTI ID:49289

Tao, G; King, M S; Nabi-Bidhendi, M ^[1]

---

1. Imperial College of Science, Technology and Medicine, London (United Kingdom). Dept. of Mineral Resources Engineering

Compressional and shear-wave velocities have been measured and a novel approach using digital processing employed to study wave attenuation for brine- and gas-saturated sandstones, over a range of effective stresses from 5 to 60 MPa. Also measured were the complex conductivity in the brine-saturated state and permeability in the gas-saturated state over the same range of stresses as for the velocity measurements. Broadband ultrasonic pulses of P- and orthogonally polarized S-waves in the frequency range 0.3--0.8 MHz are transmitted through the specimen to be characterized for comparison with a reference (aluminium) having low attenuation. The attenuation is calculated in terms of the quality factor Q from the Fourier spectral ratios, using the frequency spectral ratios technique. The corrections necessary for the effects of diffraction due to the finite size of the ultrasonic transducers have been carried out for the case of measurements under lower confining stress. To interpret the laboratory measured velocity and attenuation data under the physical conditions of this study and to estimate the effects of pore structure, numerical modeling of velocities and attenuation as functions of the confining stress have been performed, based on the MIT model. Theoretical models based on several hypothesized attenuation mechanisms are considered in relation to laboratory data of the effects of confining pressure, fluid saturation and pore structure on attenuation. Numerical calculation using these models with the experimental data indicate that friction on thin cracks and grain boundaries is the dominant attenuation mechanism for dry and brine-saturated sandstones at low effective stresses for the frequencies tested.

• Sponsoring Organization: USDOE
• OSTI ID: 49289
• Journal Information: Geophysical Prospecting, Journal Name: Geophysical Prospecting Journal Issue: 3 Vol. 43; ISSN GPPRAR; ISSN 0016-8025
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
58 GEOSCIENCES
BENCH-SCALE EXPERIMENTS
CORRECTIONS
MATHEMATICAL MODELS
NATURAL GAS DEPOSITS
NUMERICAL ANALYSIS
RESERVOIR ROCK
RESPONSE FUNCTIONS
SEISMIC SURVEYS
SEISMIC WAVES
ULTRASONIC WAVES
WAVE PROPAGATION