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Seismic evidence for an extensive gas-bearing layer at shallow depth, offshore from Prudhoe Bay, Alaska

January 1, 1980

High resolution seismic reflection data recorded offshore from Prudhoe Bay, Alaska, were processed digitally to determine the reflectivity structure of the uppermost layers of the seafloor. A prominent reflector found at 27 m below the mudline (water depths 7-9 m) has a negative reflection coefficient greater than 0.5. The large acoustic impedance contrast, coupled with a report of gas encountered at a corresponding depth in a nearby drillhole, shows that the reflector is the upper boundary of a zone containing gas. The gas exists in sandy gravel capped by stiff, silty clay. Analysis of unprocessed conventional high-resolution records from the region indicates that the gas-bearing layer may extend over an area of at least 50 km at depths of 19-35 m below the mudline. Similar-appearing reflectors, previously unexplained, occur in patches over wide regions of the shelf where offshore oil development is beginning at a rapid pace. This suggests the exercise of caution with respect to possible hazards from shallow gas pockets.

Publication Year 1980
Title Seismic evidence for an extensive gas-bearing layer at shallow depth, offshore from Prudhoe Bay, Alaska
DOI 10.3133/ofr80809
Authors Gary Wynn Boucher, Erk Reimnitz, Edward W. Kempema
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 80-809
Index ID ofr80809
Record Source USGS Publications Warehouse