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Snyder, Fred F.C.1, Lecia K Muller1, Nader Dutta1, Deborah R Hutchinson2, Patrick E Hart3, Myung W Lee4, Brandon Dugan2, Carolyn Ruppel5, Warren T Woods6, Richard Coffin7, R Evans8, Emrys H. Jones9
(1) Schlumberger RS/DCS, Houston, TX 
(2) U.S. Geological Survey, Woods Hole, 
(3) U.S. Geological Survey, Menlo Park, CA 
(4) U.S. Geological Survey, Denver, CO
(5) Georgia Tech, Atlanta, GA
(6) Naval Research Laboratory, Stennis Space Center, 
(7) Naval Research Laboratory, Washington, 
(8) WHOI, Woods Hole, 
(9) ChevronTexaco, Houston, TX

ABSTRACT: Seismic Analysis and Characterization of Gas Hydrates in the Northern Deepwater Gulf of Mexico

The deepwater Gulf of Mexico contains many known hydrate environments. Complex lithostratigraphy and active salt movement create complicated thermal regimes and fluid chemistry. These in turn affect hydrate formation and distribution. In an effort to study and eventually test different hydrate settings, two separate areas were selected for review by a multi-disciplinary team. Reprocessed 3D and high-resolution 2D multichannel seismic data were analyzed over Keathley Canyon block 195 and Atwater Valley block 14, both of which are in water depths of approximately 1300 meters. Keathley Canyon exhibits a deep (250 to 500 meters sub-seafloor), pronounced regional bottom simulating reflector (BSR), a notable geologic and geophysical barrier between free gas and solid hydrate. The BSR is bounded to the east by a salt-produced fault ridge, which is also a probable fluid migration pathway. The BSR has reverse polarity relative to the water bottom interface and obliquely cuts stratigraphic reflections. In some areas the BSR is also defined by periodic, high amplitude terminations of free gas in the coarser-grained, interbedded sands below. The Atwater Valley study area is located in the middle of the Mississippi Canyon and contains numerous hydrate mound features. Most mounds show strong seismic evidence of hydrates including gas chimneys, amplitude blanking, and near-seafloor BSRs. The complexity and diversity of all these hydrate occurrences clearly drives the need for a cross-disciplinary approach. This paper will outline the problems faced by the team, review work to date and discuss future plans.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.