Attenuation can be extremely valuable in characterizing gas accumulations in shales and sandstones. Laboratory studies clearly indicate that attenuation is closely related to fluid saturation and mobility. Well-log analysis shows that P-wave attenuation is higher in gas-bearing rocks than in those saturated with oil or water. Extremely low P-wave quality factors (Q), ranging between 5 and 10, have been observed in some gas reservoirs. For example, such low Q values in gas sands are reported by Mavko and Dvorkin (2005) in well logs from the Gulf Coast.