Seismic Attenuation in Realistic Fracture Networks

Using our newly developed finite-element solution of the quasi-static frequency-domain poroelastic equations, we conduct compressibility tests on synthetic fractured rock samples to study P-wave attenuation and velocity dispersion related to wave-induced fluid flow (WIFF). Our algorithm allows to generate realistic stochastic fracture networks and to mesh them without any user-interaction. Experiments on sets of fracture networks randomly drawn from a power-law distribution show that attenuation due to WIFF between the fractures and the background shifts to lower frequencies with decreasing fracture density, because the average distance between the fractures increases. Furthermore, we observe that attenuation due to WIFF between connected fractures shifts to higher frequencies when the average fracture length decreases, because the average distance between a fracture tip and an intersection with another fracture decreases. Our results also show that attenuation increases in magnitude with increasing average fracture length. Finally, there is preliminary evidence to suggest that attenuation may decrease for percolating fracture networks.