In addition to investigations about the cause and properties of the BSR, several attempts have been made in estimating the amount of hydrate from seismic velocities and amplitudes. Most studies determined the desired hydrate saturations using Wyllie's time average equation Wyllie et al. (1958), which directly relates acoustic velocity to porosity and saturation Korenaga et al. (1997); Sholl and Hart (1993); Wood et al. (1994). In order to obtain a more reliable estimate in high-porosity sediments, Dillon et al. 1993 used a weighted mean of the Wyllie equation together with Wood's equation 1941.
Wyllie's equation has been obtained empirically for consolidated reservoir rocks ad cannot be used for high-porosity unconsolidated sediments Dvorkin and Nur (1998). In order to apply this equation to high-porosity marine sediments, calibration is required based on extensive core measurements or well-log data. Results are modified ``time-average-form'' equations. It is likely that such equations can indeed link velocity to porosity and gas hydrate content if they have been derived from an extensive experimental database. However, such equations cannot be used for diagnosing sediments, i.e., inferring their internal structure from seismic.
Yuan et al. 1996 first derived a relation between velocity and porosity from core and well-log data. They calculated a porosity profile from velocities across a BSR and subtracted from it the ``normal'' porosity profile of sediments without a BSR. The resulting relative porosity reduction above the BSR was attributed purely to the presence of methane hydrate in the pores, which directly translates into hydrate saturation.
All of these investigations estimated 1-D hydrate saturation profiles and assumed known a-priori porosity based on well or core information. Little work has been done in considering the actual effect of the position of hydrate in the pore space and in constructing physical rock models. Furthermore, the effect of different models on seismic waveforms and amplitudes needs to be considered in order to connect a specific hydrate saturation reliably to the seismic data.