Testing Gassmann Fluid Substitution Using Sonic Logs and Core Measurements in a Sandstone Reservoir

2008 ◽  
Author(s):  
M. Grochau ◽  
M. Gurevich
Keyword(s):  
Fluid Substitution ◽  
Sandstone Reservoir ◽  
Gassmann Fluid Substitution ◽  
Sonic Logs

scholarly journals Modelling the seismic responses of Amangihydrocarbon field using Gassmann fluid substitution

2014 ◽  
Vol 2 (2) ◽  
pp. 106-114
Author(s):  
Sonny Inichinbia ◽  
◽  
Peter O. Sule ◽  
Aminu L. Ahmed ◽  
Halidu Hamza
Keyword(s):  
Fluid Substitution ◽  
Seismic Responses ◽  
Gassmann Fluid Substitution

Elastic moduli of dry and water-saturated carbonates — Effect of depositional texture, porosity, and permeability

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. N65-N78 ◽  
Author(s):  
Ida L. Fabricius ◽  
Gregor T. Bächle ◽  
Gregor P. Eberli
Keyword(s):  
Frequency Ratio ◽  
Elastic Moduli ◽  
Reference Frequency ◽  
Fluid Substitution ◽  
Water Softening ◽  
Effect Of Water ◽  
Porosity And Permeability ◽  
Gassmann Fluid Substitution ◽  
Water Saturated ◽  
Frequency Ratios

Elastic moduli of water-saturated sedimentary rocks are in some cases different from moduli derived using Gassmann fluid substitution on data for rocks in the dry state. To address this discrepancy, we use a data set representing 115 carbonate samples from different depositional settings and a wide range of porosity and permeability. Depositional texture is reflected in the effect of water on elastic moduli and in the porosity-permeability relationship. Depositional texture is taken into account when porosity and permeability are combined in the effective specific surface of pores, which is related for a given pore fluid to the reference frequency as defined by Biot. For a given frequency of elastic waves, we obtain Biot’s frequency ratio between measured ultrasonic wave frequency and Biot reference frequency. For mostsamples with a frequency ratio above 10, elastic moduli in the water-saturated case are higher than predicted from elastic moduli in the dry case by Gassmann fluid substitution. This stiffening effect of water in some cases may be described by Biot’s high-frequency model, although in heterogeneous samples, a squirt mechanism is more probable. For data representing frequency ratios of 0.01 to 1, Gassmann fluid substitution works well. For samples with frequency ratios below 0.001, elastic moduli in the water-saturated case are lower than would be expected according to Gassmann’s equations or to Biot’s theory. This water-softening effect becomes stronger with decreasing frequency ratio. Water softening or stiffening of elastic moduli may be addressed by effective-medium modeling. In this study, we used the isoframe model to quantify water softening as a function of frequency ratio.

An Integrated Analysis of Petrophysics, Cross-Plots and Gassmann Fluid Substitution for Characterization of Fimkassar Area, Pakistan: A Case Study

2014 ◽  
Vol 40 (1) ◽  
pp. 181-193 ◽  
Author(s):  
Aamir Ali ◽  
Muhammad Kashif ◽  
Matloob Hussain ◽  
Jamil Siddique ◽  
Irfan Aslam ◽  
...  
Keyword(s):  
Integrated Analysis ◽  
Fluid Substitution ◽  
Gassmann Fluid Substitution

Fluid-solid substitution in rocks with disconnected and partially connected porosity

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. WB89-WB95 ◽  
Author(s):  
Vladimir Grechka
Keyword(s):  
Pore Space ◽  
Fluid Substitution ◽  
Analytic Proof ◽  
Numerical Tests ◽  
Aspect Ratios ◽  
Effective Elasticity ◽  
Self Similar ◽  
Gassmann Fluid Substitution

It is usually believed that Gassmann fluid substitution can be performed only for a fully interconnected portion of the pore space. While this is certainly true, the presence of disconnected porosity does not necessarily invalidate Gassmann’s predictions. This unconventional view is supported with an analytic proof of the equivalence of Gassmann theory and the noninteraction approximation for the effective elasticity of solids with isolated self-similar pores. Numerical tests for more realistic microgeometries, where pores have diverse shapes and the pore space is partially disconnected, demonstrate that errors in Gassmann-type infill substitution are typically small and unlikely to exceed a few percent as long as the aspect ratios of pores are greater than approximately 0.2. If the fracture-like pores are aligned or elasticities of the substituted infills are close, Gassmann theory remains accurate for isolated pores with smaller aspect ratios.

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