EG06 P: Investigation of seismic wave attenuation in carbonate rocks

Seismic wave attenuation has a great potential for studying saturated and fractured media, due to its high sensitivity to the geotechnical properties of geological media. However, getting an accurate estimation of this parameter is challenging due to its high sensitivity to seismic noise, particularly in heterogeneous media such as saturated and fractured carbonate media. This explains the few numbers of attenuation studies carried out in carbonate rocks compared to sandstones, and still existing ambiguity about attenuation mechanism. To add more light on the topic, we conducted an experimental study to generate ultrasonic waveform signals (0.5-3 MHz) reordered under dry and fully saturation conditions in thirteen samples covering a wide range of geotechnical properties, and subjected them to effective pressure. The resulting increase in attenuation magnitudes and their variation with pressure due to brine saturation were more pronounced than in velocity magnitudes, confirming the higher sensitivity of attenuation to fluid content. However, understanding the relationship between attenuation and geotechnical properties required a careful examination of the results and a good understanding of attenuation mechanism. We suggested that multiple attenuation mechanisms coexist in carbonate rocks, including scattering, cracks slipping, solid frictional relative motion, global and squirt flow.