HR: 16:45h
AN: OS42C-04    [PDF]
TI: Evidence of subsurface gas hydrate in the northern Gulf of Mexico
AU: * Hutchinson, D R
EM: dhutchinson@usgs.gov
AF: USGS, 384 Woods Hole Rd., Woods Hole, MA 02543
AU: Hart, P E
EM: hart@usgs.gov
AF: USGS, 345 Middlefield Rd, Meno Park, CA 94025
AU: Snyder, F
EM: fsnyder@slb.com
AF: WesternGeco, 3750 Briarpark Dr., Houston, TX 77042
AU: Lee, M W
EM: mlee@usgs.gov
AF: USGS, Denver Federal Center, Denver, CO 80225
AU: Dutta, N
EM: ndutta@westerngeco.com
AF: WesternGeco, 3750 Briarpark Dr., Houston, TX 77042
AU: Muller, L
EM: lmuller@slb.com
AF: WesternGeco, 3750 Briarpark Dr., Houston, TX 77042
AU: Dugan, B
EM: bdugan@usgs.gov
AF: USGS, 384 Woods Hole Rd., Woods Hole, MA 02543
AU: Ruppel, C D
EM: cdr@piedmont.eas.gatech.edu
AF: Georgia Tech, Earth and Atmospheric Sciences, Atlanta, GA 30332
AU: Wood, W
EM: wwood@nrlssc.navy.mil
AF: NRL, Stennis Space Center, Stennis Space, MS 39529
AU: Coffin, R
EM: rcoffin@ccs.nrl.navy.mil
AF: NRL, 4555 Overlook Ave, Washington, DC 20375
AU: Evans, R
EM: revans@whoi.edu
AF: WHOI, 364 Woods Hole Rd, Woods Hole, MA 02543
AU: Jones, E
EM: ejones@chevrontexaco.com
AF: Chevron/Texaco, 2811 Hayes Rd., Houston, TX 77082
AB: The northern Gulf of Mexico is characterized by an extremely heterogeneous near-surface geology that makes geophysical identification of subsurface gas hydrate challenging and ambiguous. Bottom Simulating Reflections (BSRs) are rarely reported. A recent multidisciplinary suite of geophysical and geological observations at two sites provides examples of possible subsurface hydrate occurrence in 1350 m water depth at two different geologic settings. At the first site, near Keathley Canyon block 195, a distinct BSR over a region of 15 km2 occurs at the transition between a salt-withdrawal basin and its flanking salt-cored structural high. Analyses of 3D and high-resolution 2D multichannel seismic data show that the distribution and strength of the BSR may correlate to alternating fine and coarser-grained layers and to the geometry of faults, which presumably influence migration of warm, gas-rich fluids. Thermal gradients are variable and geochemistry indicates that hydrate may exist at depth. The second site, near Atwater Valley block 14, lies within the Mississippi Canyon and contains several sea-floor mounds. Seismic analysis of mound "F," which may be a vent, has a BSR that is significantly shallower beneath the center of the mound than it is beneath the flanks of the mound. The mound is underlain by free gas that causes ~40 ms of velocity pull-down on a sub-horizontal reflection. An integrated, multidisciplinary approach that constrains the geometry, geochemistry, and rate of fluid flux is essential for understanding the dynamics of gas hydrate systems in these different environments.
DE: 3025 Marine seismics (0935)
DE: 3099 General or miscellaneous
DE: 4820 Gases
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting