The seismic response to overpressure versus gas hydrate and free gas concentration

We propose a procedure to estimate the gas hydrate and the free gas concentration in the pore space by using jointly different information: P-wave velocity, Poisson's ratio, PP- and P- to S-reflection coefficients versus offset. The theory takes into account the possible. cementation of grain caused by the presence of hydrates, describes the distribution of free gas in the pore space (uniform or patchy). The overpressure condition in the free gas zone is considered. The method is applied in a real case (South Shetland margin, Antarctica), where multichannel seismic and ocean bottom seismometer data are collected. We estimate the gas hydrate and free gas amounts and the pore pressure. The proposed procedure can be used to determine the distribution of gas hydrate and free gas, and the pressure regime at regional scale.