Ruppel, C.1, D Hutchinson2, B Dugan2, P Hart3
(1) Earth and Atmospheric Sciences, Georgia Tech, Atlanta, GA
(2) U.S. Geological Survey, Woods Hole,
(3) U.S. Geological Survey, Menlo Park,
ABSTRACT: Predicting the Subsurface Distribution of Gas Hydrate in the Northern Gulf of Mexico
The subsurface distribution of methane hydrate in the vicinity of Keathley Canyon block 195 in the northern Gulf of Mexico can be predicted by combining two new data sets: Marine heat flow data collected under the auspices of the DOE Joint Industry Project (JIP) for Methane Hydrates and high-resolution multichannel seismic data acquired by the USGS in Spring 2003, data that image a bottom simulating reflector (BSR). Thermal gradients at the site vary from ~30 mK/m to 50 mK/m over distances as short as 500 m along transects that cross faults and high permeability fluid conduits imaged on the seismic lines. The variability in thermal regimes reflects system heterogeneity at every hydrologic scale and the complex flow of fluids (including gas) from greater depths, factors that also affect the formation of gas hydrate. If the near-seafloor thermal gradients continue unchanged to greater depths, lateral differences of up to 225 meters in the potential thickness of the gas hydrate zone would occur, assuming methane as the hydrate former. Abrupt horizontal variations in thermal gradients over short baselines can also lead to complex fluid circulation patterns that are often ignored in one-dimensional models of gas hydrate systems. Seismic constraints on the distribution and depth of the BSR and on stratigraphic and tectonic flow pathways, combined with thermal gradient and thermal conductivity results, can be used to predict the locations of concentrated and disseminated hydrate and changes in the thickness of the zone actually occupied by gas hydrate.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.