--> Abstract: Gas Hydrate Surface Simulating Seismic Reflector in the Prudhoe Bay-Kuparuk River Region of Northern Alaska, by T. S. Collett and K. J. Bird; #90987 (1993).

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COLLETT, TIMOTHY S., U.S. Geological Survey, Denver, CO; and KENNETH J. BIRD, U.S. Geological Survey, Menlo Park, CA

ABSTRACT: Gas Hydrate Surface Simulating Seismic Reflector in the Prudhoe Bay-Kuparuk River Region of Northern Alaska

Access to approximately 200 km of multichannel seismic data in the Prudhoe Bay-Kuparuk River region, courtesy of the Exxon Company, provides new insight into the structural and stratigraphic framework of this area. These are the first modern seismic data available to us in this region; they represent a significant addition to our study of gas hydrates in the Sagavanirktok Formation, a project partly funded by the U.S. Department of Energy. Preliminary analysis of the seismic data confirms the northeast-trending regional dip and northward-expanding thickness of the Sagavanirktok Formation. The clinoform style of progradation, well demonstrated to the west in the National Petroleum Reserve in Alaska, continues through the Prudhoe Bay-Kupamk River region: the Sagavanirktok representing t e topset and the coeval Canning Formation representing the foreset and bottomset parts of the clinoform sequence.

In the region of the Prudhoe Bay oil field, prominent flat-lying reflectors, which occur discontinuously at about 0.7 seconds (two-way travel time), cut across northeasterly dipping reflectors that mark the regional dip of the Sagavanirktok Formation. Preliminary analysis reveals that these flat-lying reflectors are at a depth of about 950 m, approximately coincident with the calculated base of the methane hydrate stability zone in this area; assuming a surface temperature of -11 degrees C and a subpermafrost geothermal gradient of 2.0 degrees C/100 m. In the marine environment, prominent reflectors coincident with the base of the hydrate stability zone are well known (bottom simulating reflectors, BSR's) and are postulated to be the result of free gas trapped below hydrate-bearing se iments. The reflectors observed on the seismic section over the Prudhoe Bay oil field appear to be the onshore equivalent of a BSR. We have named this newly discovered onshore BSR a surface simulating seismic reflector or SSR.

As production from the Prudhoe Bay and other North Slope oil fields declines, the exploration for new hydrocarbon resources will become increasingly important. Future hydrocarbon plays will consist of subtle structural-stratigraphic traps and other traps unique to the Arctic region, such as gas hydrates. Production of these hydrocarbon resources presents a major challenge and will require innovative approaches and new thinking. Understanding the physical and geochemical properties of SSR's will provide insight into a vast new energy resource in the Arctic.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.