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Effect of Strain-Gage-Scale Inhomogeneity On Measuring Young’s Modulus At Low Frequency
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
Summary
We have conducted laboratory experiments at seismic frequency (2–100Hz) to examine the effect of strain-gage-scale inhomogeneity on Young’s modulus measurements when using the stress-strain method. The length of the strain gage is ∼5mm, much smaller than that of samples (aluminum, Plexiglas and a tight sandstone). The aluminum sample and the Plexiglas sample are regarded as homogeneous on the strain gage scale. The Young’s modulus measured at different positions of the aluminum and Plexiglas samples shows little difference. For the tight sandstone fully saturated with oil, which is inhomogeneous on the strain gage scale, the Young’s modulus appears to show a large difference between measurements at two different positions. Both the Young’s modulus and attenuation measurements are verified to be reliable using the Kramers-Kronig relationship. As a sample exhibits inhomogeneity on the strain gage scale, the modulus measured just represents local property instead of the effective homogeneous property. This finding has profound implications how we should measure the elastic and inelastic properties of ‘effective homogeneous’ samples. We will further investigate how to estimate these properties of such samples in the low frequency range in the laboratory.
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