Seismic Velocity Structure at the Gas Hydrate Reflector - Indonesia and Pakistan

This paper describes the experimental processing of foor seismic lines, in which we attempted to learn more about the transition to and from a phase in which gas is trapped in the foren of a methane hydrate . The gas hydrate phase occurs in a temperature/pressure regime that is typically found a few hundred metres below a deep water seafloor . The transition is expressed as a so-called Bottom Simulating Reflector (BSR) ; so named because its structure mimics that of the seafloor rather than follówing the local bedding direction. Indeed reflections associated with bedding planes often cross through the BSR . In addition to the BSR, we looked for changes in seismic interval velocity, amplitude and AVO effects in the neighbourhood of the BSR. All of these help us to glean information about the nature of the gas hydrate, its generation and the hydrate / free-gas transition .