Variation in P-wave modulus with frequency and water saturation: Extension of dynamic-equivalent-medium approach

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D479-D494 ◽  
Author(s):  
Yuki Kobayashi ◽  
Gary Mavko
Keyword(s):  
Wave Velocity ◽  
Velocity Dispersion ◽  
Water Saturation ◽  
P Wave ◽  
Mesoscopic Scale ◽  
Original Theory ◽  
Saturated Rock ◽  
Pressure Diffusion ◽  
P Wave Velocity ◽  
Dynamic Equivalent

We have developed a new modeling approach for the complex-valued P-wave modulus of a rock saturated with two-phase fluid accounting for the variation with frequency and water saturation. Our method is based on the dynamic-equivalent-medium approach theory, which predicts P-wave modulus dispersion due to mesoscopic-scale wave-induced fluid flow (WIFF). Although the application of the original theory was limited to small fluctuation media, we have extended it to also be applicable for high-fluctuation media such as partially saturated rock. Our modification and extension consists of two components. The first is introducing a scaling by the rigorous bounds for P-wave velocity dispersion by mesoscopic-scale WIFF. The second is to develop a model representing the effective patch size of stiffer fluid that controls the location of the dispersion curve. We have found that the spatial correlation length of heterogeneity of saturated rock used in the original theory does not appropriately capture the effective heterogeneity scale responsible for mesoscale pressure diffusion. Its variation with saturation can be properly accounted for by the proposed patch-sized variation model. The comparison of the theoretical prediction with the published laboratory velocity and attenuation measurements suggests that our approach predicts the wave properties for high-fluctuation media with reasonable accuracy. The effect of mesoscopic-scale pressure diffusion is significant and the amount of velocity dispersion and attenuation is large in high-fluctuation media; therefore, our extension will improve quantitative characterization of, for example, a [Formula: see text]-sequestrated reservoir either by P-wave velocity or attenuation.

Effects of ellipsoidal heterogeneities on wave propagation in partially saturated double-porosity rocks

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. WC71-WC81 ◽  
Author(s):  
Weitao Sun ◽  
Fansheng Xiong ◽  
Jing Ba ◽  
José M. Carcione
Keyword(s):  
Wave Propagation ◽  
Aspect Ratio ◽  
Wave Velocity ◽  
Velocity Dispersion ◽  
Laboratory Data ◽  
P Wave ◽  
Lagrange Equations ◽  
Wave Dissipation ◽  
P Wave Velocity ◽  
The Impact

Reservoir rocks are heterogeneous porous media saturated with multiphase fluids, in which strong wave dissipation and velocity dispersion are closely associated with fabric heterogeneities and patchy saturation at different scales. The irregular solid inclusions and fluid patches are ubiquitous in nature, whereas the impact of geometry on wave dissipation is still not well-understood. We have investigated the dependence of wave attenuation and velocity on patch geometry. The governing equations for wave propagation in a porous medium, containing fluid/solid heterogeneities of ellipsoidal triple-layer patches, are derived from the Lagrange equations on the basis of the potential and kinetic energies. Harmonic functions describe the wave-induced local fluid flow of an ellipsoidal patch. The effects of the aspect ratio on wave velocity are illustrated with numerical examples and comparisons with laboratory measurements. The results indicate that the P-wave velocity dispersion and attenuation depend on the aspect ratio of the ellipsoidal heterogeneities, especially in the intermediate frequency range. In the case of Fort Union sandstone, the P-wave velocity increases toward an upper bound as the aspect ratio decreases. The example of a North Sea sandstone clearly indicates that introducing ellipsoidal heterogeneities gives a better description of laboratory data than that based on spherical patches. The unexpected high-velocity values previously reported and ascribed to sample heterogeneities are explained by varying the aspect ratio of the inclusions (or patches).

Forced imbibition into a limestone: measuring P-wave velocity and water saturation dependence on injection rate

2014 ◽  
Vol 62 (5) ◽  
pp. 1126-1142 ◽  
Author(s):  
Sofia Lopes ◽  
Maxim Lebedev ◽  
Tobias M. Müller ◽  
Michael B. Clennell ◽  
Boris Gurevich
Keyword(s):  
Wave Velocity ◽  
Water Saturation ◽  
Injection Rate ◽  
P Wave ◽  
P Wave Velocity

scholarly journals Effects of Saturation Levels on the Ultrasonic Pulse Velocities and Mechanical Properties of Concrete

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 152
Author(s):  
Ma. Doreen Esplana Candelaria ◽  
Seong-Hoon Kee ◽  
Jurng-Jae Yee ◽  
Jin-Wook Lee
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Wave Velocity ◽  
Water Saturation ◽  
P Wave ◽  
Saturation Level ◽  
Saturation Condition ◽  
P Wave Velocity ◽  
Compressive Strength Of Concrete ◽  
The Relationship

The main objective of this research is to investigate the effect of water content in concrete on the velocities of ultrasonic waves (P- and S-waves) and mechanical properties (elastic modulus and compressive strength) of concrete. For this study, concrete specimens (100 mm × 200 mm cylinders) were fabricated with three different water-to-binder ratios (0.52, 0.35, and 0.26). These cylinders were then submerged in water to be saturated in different degrees from 25% to 100% with an interval of 25% saturation. Another set of cylinders was also oven-dried to represent the dry condition. The dynamic properties of concrete were then assessed using a measurement of elastic wave accordance with ASTM C597-16 and using resonance tests following ASTM C215-19, before and after immersion in water. The static properties of saturated concrete were also assessed by the uniaxial compressive testing according to ASTM C39/C39M-20 and ASTM C469/C469M-14. It was observed that the saturation level of concrete affected the two ultrasonic wave velocities and the two static mechanical properties of concrete in various ways. The relationship between P-wave velocity and compressive strength of concrete was highly sensitive to saturation condition of concrete. In contrast, S-wave velocity of concrete was closely correlated with compressive strength of concrete, which was much less sensitive to water saturation level compared to P-wave velocity of concrete. Finally, it was noticed that water saturation condition only little affects the relationship between the dynamic and elastic moduli of elasticity of concrete studies in this study.

scholarly journals Influence of water saturation on ultrasonic P-wave velocity in weakly compacted sandstone

2017 ◽  
Vol 795 ◽  
pp. 012012 ◽  
Author(s):  
Thaqibul Fikri Niyartama ◽  
Umar Fauzi ◽  
Fatkhan
Keyword(s):  
Wave Velocity ◽  
Water Saturation ◽  
P Wave ◽  
P Wave Velocity ◽  
Influence Of Water

scholarly journals Non-Embedded Ultrasonic Detection for Pressure Cores of Natural Methane Hydrate-Bearing Sediments

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1997
Author(s):  
Xingbo Li ◽  
Yu Liu ◽  
Hanquan Zhang ◽  
Bo Xiao ◽  
Xin Lv ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Water Saturation ◽  
Hydrate Formation ◽  
Compressional Wave ◽  
P Wave ◽  
Ultrasonic Detection ◽  
Initial Water ◽  
P Wave Velocity ◽  
Hydrate Saturation

An apparatus for the analysis of pressure cores containing gas hydrates at in situ pressures was designed, and a series of experiments to determine the compressional wave response of hydrate-bearing sands were performed systematically in the laboratory. Considering the difficulties encountered in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples, the laboratory approach enabled closer study than the marine environment due to sample recovery problems. The apparatus was designed to achieve in situ hydrate formation in bearing sediments and synchronous ultrasonic detection. The P-wave velocity measurements enabled quick and successive ultrasonic analysis of pressure cores. The factors influencing P-wave velocity (Vp), including hydrate saturation and formation methodology, were investigated. By controlling the initial water saturation and gas pressure, we conducted separate experiments for different hydrate saturation values ranging from 2% to 60%. The measured P-wave velocity varied from less than 1700 m/s to more than 3100 m/s in this saturation range. The hydrate saturation can be successfully predicted by a linear fitting of the attenuation (Q−1) to the hydrate saturation. This approach provided a new method for acoustic measurement of the hydrate saturation when the arrival time of the first wave cannot be directly distinguished. Our results demonstrated that the specially designed non-embedded ultrasonic detection apparatus could determine the hydrate saturation and occurrence patterns in pressure cores, which could assist further hydrate resource exploration and detailed core analyses.

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