Modelling P-Wave Propagation in a Medium With Multiple Parallel Fractures and Direct Comparison With Experimental Recordings.

We examine P-wave propagation in a fractured medium using effective medium, explicit fractures, and localized effective medium representations of fracturing, to quantify their effectiveness. We model a published experiment with multiple parallel fractures. Initial models assume uniform fracture stiffness across all fractures. A methodology is presented for inverting a source from the experiment. We find that the waveforms from the three models do not match each other. For propagation parallel to the fractures, the explicit model performs best with excellent agreement with the experimental waveform. The waveform from the localized TI model is reasonably similar, matching arrival, predominant period, frequency content, but not amplitude. The TI model is a poor match with significant differences in period, amplitude and high frequency content. For perpendicular propagation, none of the models properly match the experimental waveform. All models reproduce the significant delay in arrival, but only the explicit and local TI models produce a reduction in period and frequency content mimicking the experiment. All models produce a reduction in amplitude but not to the degree of the experiment. An explicit model accounting for the effect of the non-uniform stress-field better matches the experiment, indicating similar developments are needed for the other two representations.