Abstract
Earlier studies on dry, clay free sandstone have shown a linear increase in the non-elastic compliance upon
unloading, apparently starting from zero at the turning point of the stress path. It is argued that the offset seen at the turning point in other rocks may be interpreted as a result of dispersion. A method, based on this assumption, for estimation of the velocity dispersion in the range from seismic to ultrasonic frequencies, using only standard rock mechanical tests with acoustic velocity measurements is presented. Application of the method is demonstrated by experimental data. The results show no measurable
dispersion in a clay free sandstone, and relatively large dispersion in a shale. The results for a sandstone with some clay content show moderate dispersion, and also indicate that the dispersion decreases with increasing stress. The method requires good quality data, but the requirement for accuracy is not extreme.
unloading, apparently starting from zero at the turning point of the stress path. It is argued that the offset seen at the turning point in other rocks may be interpreted as a result of dispersion. A method, based on this assumption, for estimation of the velocity dispersion in the range from seismic to ultrasonic frequencies, using only standard rock mechanical tests with acoustic velocity measurements is presented. Application of the method is demonstrated by experimental data. The results show no measurable
dispersion in a clay free sandstone, and relatively large dispersion in a shale. The results for a sandstone with some clay content show moderate dispersion, and also indicate that the dispersion decreases with increasing stress. The method requires good quality data, but the requirement for accuracy is not extreme.