The effect of viscoelasticity and microplasticity on the P- wave attenuation in dry and water-saturated sandstone: An experimental study

Data of experimental study of amplitude dependence of P-wave attenuation in the dry and watersaturatedsandstone under confining pressure of 10 MPa are presented. Measurements were conducted on samples using the reflection method at a dominant frequency of the initial impulse of 1 MHz in the amplitude range ~ (0,3 – 2,0) 10-6. P-wave attenuation spectra, 1( , ) P Q f in the frequency range of 0,52 – 1,42 MHz in a dry and saturated sample have an appearance in the form of relaxation peak which depends on the strain amplitude. In the saturated sandstone, attenuation is greater and the attenuation peak is shifted to higher frequencies compared to the dry sandstone. With increasing amplitude, wave attenuation decreases in dry sandstone by 4,5% and in saturated – by 9%. P-wave velocity practically doesn't depend on the strain amplitude. The possible mechanism of discrete (intermittent) inelasticity which determines the waveform distortion and exerts influence on wave attenuation spectra is discussed. The received results have fundamental and applied importance for seismics, acoustics and in Earth sciences.

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Ultrasonic attenuation in Glenn Pool rocks, northeastern Oklahoma

Geophysics ◽

10.1190/1.1444348 ◽

1998 ◽

Vol 63 (2) ◽

pp. 465-478 ◽

Cited By ~ 14

Author(s):

Andrew P. Shatilo ◽

Carl Sondergeld ◽

Chandra S. Rai

Keyword(s):

Phase Velocity ◽

Reservoir Characterization ◽

Velocity Dispersion ◽

Wave Attenuation ◽

Ultrasonic Attenuation ◽

Clay Content ◽

P Wave ◽

Phase Velocity Dispersion ◽

Q Model ◽

Water Saturated

Ultrasonic P-wave attenuation and phase velocity dispersion have been estimated for 29 samples of sandstones and 13 samples of shales from a Glenn Pool oil reservoir using a pulse transmission technique. The measurements were performed under effective pressures from atmospheric to 15 MPa. There is a strong correlation between attenuation coefficient and phase velocity dispersion. Even though the observed attenuation may deviate from a “constant Q” model, it generally agrees with a minimum‐phase prediction. Attenuation in the water‐saturated sandstones increases with porosity and permeability. We found no correlation between the attenuation and clay content within the sandstone subset. Attenuation in the shales is much less than that in the sandstones. This difference may be used in reservoir characterization.

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Pore fluid effects on S-wave attenuation caused by wave-induced fluid flow

Geophysics ◽

10.1190/geo2011-0233.1 ◽

2012 ◽

Vol 77 (3) ◽

pp. L13-L23 ◽

Cited By ~ 37

Author(s):

Beatriz Quintal ◽

Holger Steeb ◽

Marcel Frehner ◽

Stefan M. Schmalholz ◽

Erik H. Saenger

Keyword(s):

Fluid Flow ◽

Wave Attenuation ◽

Pore Space ◽

Seismic Attenuation ◽

P Wave ◽

S Wave ◽

Hydrocarbon Reservoir ◽

Saturated Media ◽

Water Saturated ◽

Wave Induced

We studied seismic attenuation of P- and S-waves caused by the physical mechanism of wave-induced fluid flow at the mesoscopic scale. Stress relaxation experiments were numerically simulated by solving Biot’s equations for consolidation of 2D poroelastic media with finite-element modeling. The experiments yielded time-dependent stress-strain relations that were used to calculate the complex moduli from which frequency-dependent attenuation was determined. Our model consisted of periodically distributed circular or elliptical heterogeneities with much lower porosity and permeability than the background media, which contained 80% of the total pore space of the media. This model can represent a hydrocarbon reservoir, where the porous background is fully saturated with oil or gas and the low-porosity regions are always saturated with water. Three different saturation scenarios were considered: oil-saturated (80% oil, 20% water), gas-saturated (80% gas, 20% water), and fully water-saturated media. Varying the dry bulk and shear moduli in the background and in the heterogeneities, a consistent tendency was observed in the relative behavior of the S-wave attenuation among the different saturation scenarios. First, in the gas-saturated media the S-wave attenuation was very low and much lower than in the oil-saturated or in the fully water-saturated media. Second, at low frequencies the S-wave attenuation was significantly higher in the oil-saturated media than in the fully water-saturated media. The P-wave attenuation exhibited a more variable relative behavior among the different saturation degrees. Based on the mechanism of wave-induced fluid flow and on our numerical results, we suggest that S-wave attenuation could be used as an indicator of fluid content in a reservoir. Additionally, we observed that impermeable barriers in the background can cause a significant increase in S-wave attenuation. This suggests that S-wave attenuation could also be an indicator of permeability changes in a reservoir due to, for example, fracturing operations.

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