CONSTRAINING GAS HYDRATE OCCURRENCE IN THE NORTHERN GULF OF MEXICO CONTINENTAL SLOPE: FINE SCALE ANALYSIS OF GRAIN-SIZE IN HYDRATE-BEARING SEDIMENTS

Proceedings of the 6th International Conference on Gas Hydrates (ICGH 2008), Vancouver, British Columbia, CANADA, July 6-10, 2008. CONSTRAINING GAS HYDRATE OCCURRENCE IN THE NORTHERN GULF OF MEXICO CONTINENTAL SLOPE: FINE SCALE ANALYSIS OF GRAIN-SIZE IN HYDRATE-BEARING SEDIMENTS Alexandra Hangsterfer∗ Geosciences Research Division Scripps Institution of Oceanography 9500 Gilman Drive, Mail Code 0208 La Jolla, CA 92093 USA Neal Driscoll and Miriam Kastner Geosciences Research Division Scripps Institution of Oceanography 9500 Gilman Drive, Mail Code 0208 La Jolla, CA 92093 USA ABSTRACT Within the subseafloor, methane hydrates form within the gas hydrate stability zone (GHSZ). Two areas within the Gulf of Mexico (GOM) were investigated in this study: Keathley Canyon and Atwater Valley. The GOM contains an underlying petroleum system and deeply buried, yet dynamic salt deposits. Salt tectonics and fluid expulsion upward through the sediment column lead to the formation of fractures, through which high salinity brines migrate into the GHSZ, destabilizing gas hydrates. Originating from the thermal and biogenic degradation of organic matter, thermogenic and biogenic hydrocarbons also migrate to the seafloor along the GOM’s northern slope. Gas hydrate occurrence can be controlled by either primary permeability, forming in coarse-grained sediment layers, or by secondary permeability, forming in areas