Abstract In 1995, the U.S. Geological Survey conducted the first systematic assessment of the in-place natural-gas-hydrate resources of the United States. That study suggested that the permafrost-associated gas hydrates on the Alaska North Slope may contain as much as 590 tcf (16.7 tcm) of in-place gas. However, the Alaska North Slope gas-hydrate assessment failed to identify or characterize the nature of individual gas-hydrate accumulations or prospects. Detailed analysis and interpretation of available two-dimensional (2-D) and three-dimensional (3-D) seismic data, along with seismic modeling and correlation with specially processed downhole well-log data, have lead to the development of a viable method for identifying subpermafrost gas hydrate prospects within the gas-hydrate stability zone (GHSZ) and associated sub-gas-hydrate free-gas prospects in the Milne Point area of northern Alaska. This study has revealed a total of 14 gas-hydrate prospects in the Milne Point area. The seismic data, in conjunction with geophysical modeling results from a related study, was also used to further characterize the thickness and concentration of gas-hydrate occurrences within the delineated prospects. A Monte-Carlo-style statistical analysis of the seismic and well-log-derived reservoir data indicates that the gas-hydrate prospects in the Milne Point area may hold about 668.2 (18.9 bcm) bcf of gas.

Detailed geologic mapping and structural analysis along the northeast margin of the Wyoming overthrust belt reveals a complex interaction between the thrust belt and foreland faults and folds. Palynologic dates and structural overprinting provide the primary age control for the timing of these events: (1) late Cretaceous to early Paleocene motion on the east-directed Granite Creek thrust; (2) middle to late Paleocene movement on the east-directed Granite Creek blind thrust and the genetically related (by triangle zone) west-directed Game Hill thrust; (3) possibly early to late Paleocene motion on the foreland Cache Creek fault system on the Cache Creek “blind” fault; (4) late Paleocene to early Eocene motion on the out-of-sequence, east-directed Prospect thrust system; (5) early Eocene motion on the foreland Cache Creek subfault and Cache Creek fault of the Cache Creek fault system; and (6) late normal faulting, which truncates the above structures. Thrusts within the out-of-sequence Prospect thrust system include, from east to west, the westward-younging Cliff Creek, Little Granite Creek, Bull Creek, Game Creek, and Bear thrusts. The evolving Gross Ventre foreland uplift provided a buttress against further eastward thrusting, thus primarily causing this westward-younging thrust sequence.