Modeling seismic attenuation due to wave-induced fluid flow in the mesoscopic scale to interpret laboratory measurements

Abstract

We measured seismic attenuation in the frequency range from 1 to 100 Hz and transient fluid pressure in partially saturated Berea sandstone. The sample was saturated with 97% water (3% air). To test whether fluid flow in the mesoscopic scale was the main cause of the measured attenuation, we performed numerical modeling to compute attenuation and transient fluid pressure on a 3D poroelastic model that represents the partially saturated sample. Waveinduced fluid flow in the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerical results reproduced the laboratory data for transient fluid pressure. The numerically calculated attenuation, superposed to the frequency-independent attenuation measured in the dry rock, reproduced attenuation measured in the partially saturated sample. These results show that wave-induced fluid flow in the mesoscopic scale is the dominant mechanism for the frequencydependent component of seismic attenuation in partially saturated sandstone.