High-resolution seismic characterization of the gas and gas hydrate system at Green Canyon 955, Gulf of Mexico,USA |
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| Institution: | 1. U.S. Geological Survey Central Energy Resources Science Center, Box 25046 MS 939, Denver Federal Center, Denver, CO 80225, USA;2. U.S. Geological Survey Pacific Coastal and Marine Science Center, 2885 Mission Street 999, Santa Cruz, CA 95060, USA;3. Bureau of Ocean Energy Management, 1201 Elmwood Park Blvd, New Orleans, LA 70123, USA;4. Bureau of Ocean Energy Management, 45600 Woodland Road, Sterling, VA 20166, USA;5. University of Colorado at Boulder Department of Geological Sciences, Boulder, CO, UCB 399, Boulder, CO 80309-0399, USA;6. Department of Energy, National Energy Technology Laboratory, Morgantown, WV, USA;1. Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Taiwan;2. Ocean Center, National Taiwan University, Taiwan;3. Helmholtz Centre for Ocean Research Kiel, Germany;4. Institute of Earth Sciences, Academia Sinica, Taiwan;1. Geomar Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1–3, 24148 Kiel, Germany;2. Institute of Earth Sciences, Academia Sinica, No. 128, Academia Road, Sec. 2, Nangang Dist., Taipei, Taiwan;3. Institute of Marine Sciences and Technology, Dokuz Eylül University, Bakü Street, 35340 Inciralti, Izmir, Turkey;1. The Ohio State University, School of Earth Sciences, 317 Mendenhall Lab, 125 S. Oval Mall, Columbus, OH 43202, USA;2. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA;1. Energy Geosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA;2. Petroleum Engineering Department, Texas A&M University, College Station, TX, 77843, USA;3. U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA, 15236, USA;1. Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Sapporo, Japan;2. Methane Hydrate R&D Division, Technology and Research Center, Japan Oil, Gas and Metals National Corporation (JOGMEC), Chiba, Japan |
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| Abstract: | The Pliocene and Pleistocene sediments at lease block Green Canyon 955 (GC955) in the Gulf of Mexico include sand-rich strata with high saturations of gas hydrate; these gas hydrate accumulations and the associated geology have been characterized over the past decade using conventional industry three-dimensional (3D) seismic data and dedicated logging-while-drilling (LWD) borehole data. To improve structural and stratigraphic characterization and to address questions of gas flow and reservoir properties, in 2013 the U.S. Geological Survey acquired high-resolution two-dimensional (2D) seismic data at GC955. Combined analysis of all available data improves our understanding of the geological evolution of the study area, which includes basin-scale migration of the Mississippi River sediment influx as well as local-scale shifting of sedimentary channels at GC955 in response to salt-driven uplift, structural deformation associated with the salt uplift, and upward gas migration from deeper sediments that charges the main gas hydrate reservoir and shallower strata. The 2D data confirm that the sand-rich reservoir is composed principally of sediments deposited in a proximal levee setting and that episodes of channel scour, interspersed with levee deposition, have resulted in an assemblage of many individual proximal levee deposit “pods” each with horizontal extent up to several hundred meters. Joint analysis of the 2D and 3D data reveals new detail of a complex fault network that controls the fluid-flow system; large east-west trending normal faults allow fluid flow through the reservoir-sealing fine-grained unit, and smaller north-south oriented faults provide focused fluid-flow pathways (chimneys) through the shallower sediments. This system has enabled the flow of gas from the main reservoir to the seafloor throughout the recent history at GC955, and its intricacies help explain the distributed occurrences of gas hydrate in the intervening strata. |
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| Keywords: | Gas hydrate Seismic reflection Gulf of Mexico Gas chimney Focused fluid flow |
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