Abstract

Vast reserves of gas hydrate occur in deep oceanic environment, where the thick water column exert enough pressure to stabilize the gas hydrate. The gas hydrate is usually identi.ed on the seismic data using the bottom simulating re.ector (BSR), which mark the bottom of the hydrate stability zone. The excess gas that was captured at and beneath the base of gas hydrate stability manifest itself as free gas that is usually associated with the BSR. The presence of free gas decreases the seismic velocity and can be identi.ed in the interval velocity model. Building an accurate interval velocity models is also important for estimating the hydrate and gas saturation. The velocity can also be used for accurate seismic imaging and AVO (amplitude variation with o.set) analysis. Since the resolution of interval velocity is decreased by the presence of thick water column, I used the wave-equating datuming to remove the traveltime of the overburden so that the interval parameters can be estimated with reasonable accuracy. The algorithm makes use of the fact that the velocity of P-wave in water is known (? 1500 m/s).