Experimental determination of elastic anisotropy of Berea sandstone, Chicopee shale, and Chelmsford granite

Abstract

We use the ultrasonic transmission method to measure P-, SH-, and SV-wave velocities for Chelmsford Granite, Chicopee Shale, and Berea Sandstone in different directions up to 1000 bars confining pressure. The velocity measurements indicate that these three rocks are elastically anisotropic. The stiffness constants, dynamic Young's moduli, dynamic Poisson's ratios, and dynamic bulk moduli of these three rocks were also calculated. These elastic constants, together with velocity measurements, suggest that: (1) Elastic anisotropy is due to the combined effects of pores/cracks and mineral grain orientation. (2) Elastic anisotropy decreases with increasing confining pressure. The residual anisotropy at higher confining pressure is due to mineral grain orientation.

Integrated seismic study of naturally fractured tight gas reservoirs. Final report, September 1991--January 1995

“…Figures (10) and (11) compare low and high frequency saturated P and S velocities for transversely isotropic granite and sandstone predicted using dry pressuredependent data from Lo, et al (1986). The measured dry data are plotted as points, and the predicted values are plotted as curves.…”

Characterization of in-Situ Stress and Permeability in Fractured Reservoirs

“…For instance, Lo et al (1986) measured ultrasonic P, SH, and SV wave velocities in sample rocks of a typical granite, shale, and sandstone, while varying the confining pressure from 5 to 100 M P a. The experiments were performed for several directions of wave propagation.…”

“…The results suggest that Berea sandstone is transversely isotropic and therefore satisfies the condition of isotropicity required by the stress-induced anisotropy method. Figure 17 shows two orthogonal shear wave velocities reported in Lo et al (1986) corresponding to a perpendicular direction of propagation with respect to bedding planes. We based our next calculations on the experimental results presented in figure 17.…”

“…Figure 18: Ratios of maximum (black plus signs) and minimum (blue dots) stress to vertical stress estimated from stress-induced velocity anisotropies at crossover depths. Experimental data used as base of comparisons are elastic velocities of Berea sandstone reported in Lo et al (1986). • .…”

Shale dynamic properties and anisotropy under triaxial loading

“…This relative rareness is partly due to: (i) the inherent difficulty of transmitting transducer signals through the waterproof pressure chamber in a loading apparatus ; and, on the other hand, (ii) the specificities in preparing and handling shale samples for mechanical testing (chemical sensitivity to water, extremely low permeability...). Most of the dynamic experimental studies reported in the literature on shale samples were performed under hydrostatic loading conditions (Johnston and Toksöz 1980;Jones and Wang 1981;Lo et al 1986;Johnston and Christensen 1995;Hornby 1998;Stanley and Christensen 2001). Only Yin (1992) carried out triaxial tests.…”