A new research paper, recently  published in Geophysical Journal International,  led by G&G post graduate student Kelvin Amalokuw; with colleagues from the universities of Southampton and Edinburgh, and the British Geological Survey:

Experimental studies have shown the ratio of P- to S-wave attenuation (Q¬s/Qp ratio) to be more sensitive to gas saturation than the ratio of P- to S-wave velocity. Although this has been studied in non-fractured rocks, the effect of partial saturation on attenuation in fractured rocks is still unknown. Using synthetic, silica-cemented, sandstones with aligned penny-shaped voids (fracture density of 0.0298 ± 0.0077) to simulate the effect of fractures in the Earth according to theoretical models, we conducted laboratory ultrasonic experiments to investigate the effects aligned fractures would have on these relationships as aligned fractures are believed to be common in reservoirs. Our results for the un-fractured rock agree with published results, however, the fractured rock exhibits a different behaviour which could have potential implications on fractured rock characterisation.

Link: http://gji.oxfordjournals.org/cgi/content/abstract/ggu076?%20ijkey=jvk0LeVLGzlCsxO&keytype=ref