... 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 velocity changes in the reservoir, confirming a result of the paper by Baechle et al. The last...

... 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...

... 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 fluid. The compressional and shear-wave velocities V p and V s are given by (9) where ρ b...

...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...

... and measured acoustic logs. However, the better match transferred the problem from unknown mixing parameters to unknown 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...

...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. ...

... 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 basic assumptions...

... shaly sand to sandy shale beyond which the sand grains cease to be connected, and the clay 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...

... 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...

...). Using production information to identify gas-bearing zones, fluid substitution using the Biot-Gassman equation was performed where necessary. In addition, fluid substitution was used for zones with a strong high resistivity signature and SP expression. The Gardner and mass-balance equations were used...

... by which the macroscopic equations are derived by starting with the detailed microscale physical description. The acoustics of single-porosity media, i.e., porous media with a single pore-size characteristic length, was pioneered by Biot, who derived his model on the basis of phenomenological reasoning...

... parameters a, m, and n, respectively the tortuosity factor, cementation exponent, and saturation exponent, are set to 1, 2, and 2, respectively, in this example. The soft sand model of Dvorkin and Nur (1996) combined with Gassman’s equation ( Gassman, 1951 ; Mavko et al., 2009 ) are used to calculate...

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

... presented 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...

... 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 porosity appearing in the denominator of equation 2 . The effect...

...-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...

...]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\ V_{S}^{2}\ =\ f_{2}\left(Pe^{\frac{1}{3}}\right)\] \end{document} Equation 1 is in the same form as Gassman's equations (published in 1951) which relates porosity and bulk/shear moduli...