UC Berkeley

Historically, the presence of methane hydrate has been inferred on the basis of bottom simulating reflectors (BSRs), which are believed to mark the phase boundary between hydrate and the probable underlying free gas zone. However, in the Gulf of Mexico, laterally continuous BSRs have not been observed. The presence of laterally discontinuous vertical migration pathways may be one possible reason for the absence of BSRs in the Gulf of Mexico. To investigate this hypothesis, we use the data from a seismic survey conducted in water depth of about 1500 m. We perform a three parameter AVO inversion on the portion of the 2D seismic line in the vicinity of a salt tongue where gas hydrate accumulations may be concentrated. We identify a possible hydrate accumulation that extends 3000 m laterally from the salt flank. The hydrate reservoir is estimated to be 40 m in thickness and overlays a 20 m transition layer between hydrate and free gas. The total volume of methane gas in the reservoir is in the range of 126 to 252 billion cubic feet.