... interpreted using time-delay results as opposed to amplitude changes and (2) fluid related changes were detected in vuggy or low pore aspect ratio porosity zones but not in zones with intergranular porosity. An interesting observation of this study is that the application of Gassman's equation underpredicts...

... interactions can contribute towards significant energy loss at low and intermediate frequencies. Both the classical Gassmann's equation and the generalized Gassman's equations are inadequate in heavy-oil sand reservoirs due to the breakdown of two important underlying assumptions related to the shear...

... with no tangential stiffness. The air compressibility is accounted for when calculating the dry sand bulk modulus K ∗ with Gassman's ( Gassman, 1951 ) equation: (8) where K Air and K g are the bulk moduli of air and grain, respectively. The shear modulus ( G HM ) is not affected by pore...

...Evangelia Leon; Sarah L. Gassman; Pradeep Talwani Increase in strength due to aging of sands is reflected in higher blow counts and tip resistance values in penetration resistance measurements. This affects the magnitudes and peak ground acceleration estimates of prehistoric earthquakes obtained...

... aspect ratios ( Xu & White 1995 ). That Gassman substitution equations are not universally valid should not come as a surprise. Petrophysics has been plagued with mixing law problems in shaly sand evaluations for decades. This problem has not been fully resolved, despite eminent contributions...

...F IG . 1. P - and S -velocities for a quartz sand as a function of water saturation. The curves are calculated with Gassman's equations, assuming a burial depth of 10 m. ...

...- and S-wave velocities of different lithologic rocks ( Li, 1992 ). The expressions of the Gassman equation are shown in equations  1 – 4 ( Robert and Xu, 2002 ). The Gassmann equation is not reliable for representing the saturation effect, especially in shale. This is mainly due to several...

... with different geological ages. These channel sands are of different quality and with various shale percentages and porosities. Three cases of Gassman fluid substitution were analyzed: wet, oil, and gas. Compressional- and shear-wave impedances were calculated for the three fluid cases and Lamé parameters (λρ...

... becomes the continuous matrix. Sand porosities (ϕ) of 34% and 39% were taken as the threshold values at 40 MPa and ambient pressure, respectively. For shaly sand, a modified Gassman’s equation (1951) was used as a velocity-porosity transform; for sandy shale, Wood’s relation (1941) was shown to best fit...

... manufacturing, designing antinoise devices. When modeling transport processes in porous media, we can distinguish two kind of approaches (1) phenomenological approaches, i.e., macroscopic approaches, and (2) homogenization methods by which the macroscopic equations are derived by starting with the detailed...

... data ( Figure 5 ). Figure 5. Crossplot showing strong correlation of pseudosonic data to actual sonic data (where available). Using production information to identify gas-bearing zones, fluid substitution using the Biot-Gassman equation was performed where necessary. In addition, fluid...

... cases, the in situ background trend is shown color-coded by clay content. Within the reservoir interval, which for this example lies at approximately 2.2 km below the seafloor, Gassman’s equation ( Gassman, 1951 ; Mavko et al., 2009 ) has been used to calculate the variation in acoustic...

...Table 1. Some Parameters Used in Gassman’s Equation ...

... fraction of floating grains. This floating fraction is treated as an effective fluid and modeled via Gassman substitution, whereas the effect of the captured grains is absorbed by using the structural porosity ϕ s = ϕ + ϕ flt in β , equation 4 , and the load bearing or structural...

...-offset analysis where a very-low-frequency model is generally considered ( Gassman, 1951 ). At finite frequencies, the presence of fluid in a porous medium can cause the wave propagation to be frequency dependent and energy is lost because of viscous attenuation ( Biot, 1956 ). Studying this frequency...

..., 1991 ): The bulk modulus can be found from equations listed in Table 2 . Higher values of the density gradient can be obtained in soil when slight changes in pressure decrease the porosity and increase the density. On the other hand, smaller values of density gradient can be expected...

... in the work by Geyin and Maurer (2023) , the Shear Wave Velocity Profile Database (VSPDB) ( Kwak et al., 2021 ), South Carolina Department of Transportation (SCDOT, 2023) , Sasanakul and Gassman (2019) , and Stephenson et al. (2015) . The quality of 493 V S profiles collected from these sources...