Seismic P-wave Attenuation in Fractured Rocks

In this work, we have used numerical oscillatory compressibility simulations based on the quasi-static poroelastic equations to study the role played by fracture connectivity on the characteristics of seismic attenuation due to wave-induced fluid flow (WIFF). We verified that, in absence of fracture connectivity, mesoscale fractures oriented perpendicularly to the direction of seismic wave propagation generate important levels of attenuation, which are produced by WIFF between fractures and the embedding porous matrix. In addition, as soon as they are intersected by other fractures, the seismic signatures change rather dramatically. In particular, a decrease in the attenuation peak related to the unconnected scenario together with the appearance of an additional attenuation peak can be observed. The spatial distributions of the local energy dissipation allowed us to confirm that the additional manifestation of WIFF arising in presence of fracture connectivity is produced by fluid flow within fractures. We also corroborated that in presence of connectivity seismic attenuation is sensitive to key hydraulic parameters, namely permeabilities, lengths, aperture and intersection angle of the fractures, as well as to the connectivity degree of the fracture network. Correspondingly, a better understanding of this topic may allow to extract these key properties from seismic data.