Gas Hydrates of the Northern Gulf of Mexico from Standard Processing of Vertical Line Array and Deep-towed Data: Structural Control on Seafloor Deformation and Slope Destabilization

Bradley M. Battista, Department of Geological Sciences, University of South Carolina, 701 Sumter St, Columbia, SC 29208, phone: 803-361-4403, bbattista@geol.sc.edu, Camelia Knapp, Dept. of Geological Science, University of South Carolina, E&WS Bldg., 701 Sumter St, Columbia, SC 29208, Erika Geresi, MMRI, University of Mississippi, 220 Old Chemistry Bldg, University, MS 38677, Tom McGee, MMRI/CMRET, University of Mississippi, 220 Old Chemistry Bldg, University, MS 38677, Ross Chapman, School of Earth and Ocean Sciences, University of Victoria, P.O.Box 3055, Victoria, British Columbia, V8W 3P6, Canada, Allen Lowrie, Consultant, 238 FZ Goss Road, Picayune, MS 39466, and J. Robert Woolsey, The Center for Marine Resources and Environmental Technology, University of Mississippi, 220 Old Chemistry Building, University, MS 38677.

Advancements in the collection of acoustic reflection data including vertical line array (VLA) and shallow source, deep-towed receiver (SSDR) system in the Mississippi Canyon zone of the Gulf of Mexico allow for improved imaging and analysis of the physical properties of gas hydrates. The gas hydrates in this region form in thick, Pleistocene sediments and lack the presence of a Bottom Simulating Reflector (BSR) on previously recorded multi-channel seismic reflection data at token sites. A combined VLA/SSDR acquisition system provides accurate velocities necessary to migrate and depth-convert the SSDR data. In addition, this method proves the validity of standard seismic data processing techniques to handle these ultra-high resolution seismic data acquired in a complex geologic environment. Through specialized processing including preservation of the true reflection amplitudes, wavelet deconvolution, amplitude variation with offset (AVO), and pre-stack depth migration, results of this research include the: (1) identification of the bottom of the gas hydrate layer in the study area, (2) evaluation of the gas hydrate concentration in the host sediments, (3) recognition of shallow structural disruption and seafloor deformation possibly related to the presence of gas hydrates in the subsurface, (4) detection of methane-flux conduits in the shallow sediments and the dynamic character of the gas hydrates that dissociate and re-equilibrate rapidly across the shallow structural disruption in the sub-bottom sediments. This work proves to be suitable in gas hydrate locations with highly complex geology, thermogenic gas, and high fluid flux such as the Gulf of Mexico.

Gas Hydrate Exploitation, Sediment Strength, and Slope Instability Along Continental Margins (EMD/SEPM)
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