Experimental verification of effective anisotropic crack theories in variable crack aspect ratio medium

Abstract

A B S T R A C TPhysical modelling of cracked/fractured media using downscaled laboratory experiments has been used with great success as a useful alternative for understanding the effect of anisotropy in the hydrocarbon reservoir characterization and in the crustal and mantle seismology. The main goal of this work was to experimentally verify the predictions of effective elastic parameters in anisotropic cracked media by Hudson and Eshelby-Cheng's effective medium models. For this purpose, we carried out ultrasonic measurements on synthetic anisotropic samples with low crack densities and different aspect ratios. Twelve samples were prepared with two different crack densities, 5% and 8%. Three samples for each crack density presented cracks with only one crack aspect ratio, whereas other three samples for each crack density presented cracks with three different aspect ratios in their composition. It results in samples with aspect ratio values varying from 0.13 to 0.26. All the cracked samples were simulated by penny-shaped rubber inclusions in a homogeneous isotropic matrix made with epoxy resin. Moreover, an isotropic sample for reference was constructed with epoxy resin only. Regarding velocity predictions performed by the theoretical models, Eshelby-Cheng shows a better fit when compared with the experimental results for samples with single and mix crack aspect ratio (for both crack densities). From velocity values, our comparisons were also performed in terms of the ε, γ , and δ parameters (Thomsen parameters). The results show that Eshelby-Cheng effective medium model fits better with the measurements of ε and γ parameters for crack samples with only one type of crack aspect ratio.

Anisotropic Rock Model-Guided Post-Stack Attribute Analysis With Pore Type and Production Data for a Carbonate Gas Reservoir

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Pressure effects on the anisotropic electrical conductivity of artificial porous rocks with aligned fractures

“…Despite the broad experimental and theoretical efforts made over the years, the pressure effects on the anisotropic electrical conductivity of fractured rocks are still poorly understood. The pressure effects can be important because all geological rocks are experiencing pressure, and the changes in the pressure will directly affect the geometry and amount of fractures, which will further alter the electrical properties of the rocks where the fractures are residing (Chen et al ., 2015; Henriques et al ., 2018).…”