Ultrasonic modeling of synthetic finely layered and porous rocks: Theoretical and experimental investigation

The study of porous layered rocks is important in Earth science. Although these media can be found in almost any geological scenario, there have been few physical modeling studies (due in significant part to the difficulty in construction and elaboration) of layered media with porous and permeable layers, even though they closely resemble natural geological environments. In this study, we propose a new way for producing porous/permeable synthetic layered media to provide information about their behavior in the context of seismic wave propagation research. An experimental ultrasonic study is carried out in synthetic porous layered rocks with sequences of two alternate types of isotropic and homogeneous layers with varying physical properties simulating different lithologies. The models are subjected to ultrasonic measurements in order to determine the propagation of Pand S-waves in a transversely isotropic medium with a vertical axis of symmetry (VTI). To measure the temporal P- and S-waveforms, we use transducers with frequencies of 500 kHz and 1 MHz. The velocities were calculated perpendicular and parallel to the bedding planes. The measured velocities are compared to theoretical velocities calculated using Backus averaging and Kennett's theory. As a result of our construction procedure, pressure-related effects result in significant deviations from theoretical predictions in their measurements, particularly for those with the highest number of layers. We attempt to obtain more uniform sample compaction for this subgroup. The Backus average for 1 MHz (for P and S waves) and Kennett's hypothesis for 500 kHz (for P waves) represent the experimental results well for the samples with few layers and for the group in which the pressure is controlled.& COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

In this study, the behavior of porous layered rocks in seismic wave propagation research was investigated through experimental ultrasonic measurements. The results showed significant deviations from theoretical predictions, particularly for samples with a higher number of layers, due to pressure-related effects.