Fractures In Porous Biot Medium
We present a calculated seismic signatures of permeable fracture set in initially porous background medium. To address the problem we use approach where plane fractures are modeled as thin and soft Biot layers which in zero-thickness limit are equivalent to so called “linear slip interfaces”. Key point is that now fractures possess some permeability and they are put in medium which is itself porous and permeable. By means of matrix averaging technique developed by the authors we construct long-wave equivalent effective model for a medium with a set of parallel fractures. Assuming Biot type of loss in host and fracture materials we analyze the velocity and attenuation behavior of ordinary longitudinal wave. We found that attenuation is most informative parameter. At low seismic frequencies inverse Q has nonlinear behavior with peak and large values along fractures whereas across fractures it has linear behavior and small values.