The U.S. Geological Survey led a seismic acquisition expedition at Walker Ridge 313 (WR313) and Green Canyon 955 (GC955) in the Gulf of Mexico from April 18 through May 3, 2013, acquiring multicomponent and high-resolution 2D seismic data. WR313 and GC955 are established, world-class research sites where high gas hydrate saturations exist within reservoir-quality sands in a long-established petroleum province. Logging-while-drilling (LWD) data acquired in 2009 by the Gulf of Mexico Gas Hydrates Joint Industry Project provide detailed characterization at the borehole locations, and industry seismic data provide regional- and local-scale structural and stratigraphic characterization. Significant remaining questions regarding lithology and hydrate saturation between and away from the boreholes spurred new geophysical data acquisition at these sites. The goals of our 2013 surveys were to (1) achieve improved imaging and characterization at these sites and (2) refine geophysical methods for gas hydrate characterization.
In the area of WR313 we deployed 25 OBS and acquired approximately 450 km of streamer seismic data in a grid pattern with line spacing as small as 250 m and along radial lines that provide source offsets up to 10 km for the OBS. In the area of GC955 we deployed 21 ocean-bottom seismometers (OBS) and acquired approximately 400 km of high-resolution 2D streamer seismic data in a grid with line spacing as small as 50 m and along radial lines that provide source offsets up to 10 km and diverse azimuths for the OBS. These new data afford at least three times better vertical resolution of the structural and stratigraphic features of interest at the sites and enable considerably improved characterization of lithology and the gas and gas hydrate systems. Our recent survey represents a unique application of dedicated geophysical acquisition to the characterization of confirmed reservoir-quality gas hydrate accumulations. These new data and interpretations are important progress toward tapping into the vast global reserves of gas hydrate.
