A new gas hydrate prospect in a dipping coarse-grained reservoir in Green Canyon, US Gulf of Mexico

Abstract:

We describe a new, promising gas hydrate prospect in the Green Canyon protraction area in the US northern Gulf of Mexico in blocks GC592, GC593 and GC594. The prospect is located under the northern slope of a salt floored and salt bounded minibasin in water depths of 1270-1500 m. A well-defined bottom simulating reflection (BSR) cuts across a package of diverging dipping reflectors at a depth of ~720 msec TWT (~550 m) below the seafloor demarcating the likely base of gas hydrate stability zone (GHSZ). One of the upper dipping reflectors shows a consistent phase reversal at the base of GHSZ persisting along a ~8500 m interface between hydrate-bearing and gas-bearing units. A prominent strong peak-leading seismic response above the phase reversal likely indicates gas hydrate and occupies an area of 8.5 km2; trough-leading response below the base of GHSZ indicates gas. Another, subparallel seismic reflector likewise shows a strong peak-leading response above the base of GHSZ, yet over a smaller area. Our seismic-stratigraphic and attribute analyses show that gas hydrate accumulations occur in outer levees or overbank facies of a paleo channel depositional system, indicating that gas hydrate likely exists in a coarse-grained reservoir. Hydrate accumulations are stratigraphically trapped at the updip northern edge of the reservoir and bounded by the base of GHSZ downdip, where we also find evidence of a gas-water contact. This newly discovered gas hydrate system bears striking resemblance to the Terrebonne gas hydrate accumulation, which is planned to be drilled and pressure cored in the upcoming years. However, this new system is found in a shallower water depth (~1350 vs 2000 m), a shallower subseafloor depth (~670 vs 490 m to the shallowest gas hydrate targets) and shows a more continuous BSR and consistent peak-leading reflections. Overall, this new gas hydrate prospect is yet another promising target for potential drilling campaign and production tests.