Lutken, Carol Blanton1, Erika Geresi1, Tom McGee1, Warren T.
Wood2, A. Lowrie3
(1) University of Mississippi, University, MS
(2) Naval Research Laboratory, Stennis Space Center, MS
(3) Consultant, Picayune, MS
ABSTRACT: Complex Geology Creates Difficult Interpretational Scenarios in Hydrated Areas Along Western Flank of Mississippi Canyon, Northern Gulf of Mexico
The western flank of the Mississippi Canyon, centered about Federal Lease Block 798, in the northern Gulf of Mexico has been the center of surveying by the Center for Marine Resources and Environmental Technology, University of Mississippi. Some 50 km of high resolution and a similar amount of industry-based single channel seismics along with gravity cores and associated heat-flow data constitute their database.
Although this region offers resource potential, it is geologically complex and difficult to interpret unambiguously. Thermal measurements indicate that the seafloor is within the hydrate stability zone and that the zone may be up to 1600 ft (530 m) thick. Gas hydrate thicknesses based on regional pressure and temperature fields for methane indicate that the gas hydrate stability zone should be about 300 ft (100 m) thick, but should ethane and/or butane be present, the stability zone for hydrates of these gases could be appreciably thicker. Conversely, adjacent salt domes/ridges could be increasing the thermal gradient, and reducing gas hydrate thickness. Salinity from salts also impacts hydrate stability, and local salt abundance will be determined by fluid conduits, pressure fields, and underlying lithology and tectonics, interpretations of which may not be possible with available seismic and core data.
Combined dynamics of salt, sediments, and fluids create conditions appropriate for de-watering, fluidizing, over- and under-pressuring, compressive and extensional tectonics within restricted regions. Developing detailed quantitative models (mandatory for profitable and safe hydrate exploitation) will require different techniques and more detailed data than customarily acquired.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.