Regional Sedimentation Patterns and Hydrocarbon Potential, Eagle Plain Basin, Yukon

Kevin W. Jackson¹, Per Kent Pedersen¹, and Larry S. Lane^2
1Department of Geoscience, University of Calgary, Calgary, AB, Canada.
²Geological Survey of Canada, Calgary, AB, Canada.

The Eagle Plain Basin is a relatively unexplored intermontane basin located in northern Yukon with known petroleum systems. The objective of this study is to refine the stratigraphic framework and assess the hydrocarbon potential for the middle to upper Cretaceous succession of the Eagle Plain Basin by integrating seismic, outcrop, core, well log and petrographic data. Comparison of new data with research from adjacent basins is vital to understanding regional scale sedimentation patterns and paleogeography in northern Yukon and Northwest Territories.
Coarse-grained clastic facies are observed throughout the middle to Upper Cretaceous succession, particularly in southeastern Eagle Plain. The Albian-Cenomanian Parkin Formation consists of a basal transgressive pebbly sandstone member with high-quality reservoir characteristics, and a middle sandstone member with clean shoreface sandstones up to 20m thick in outcrop. Upward coarsening deltaic sandstone cycles in the Turonian Fishing Branch Formation tested large volumes of gas, up to 3,300 mcf/day. Facies trends, paleoflow indicators, and isopachs suggest a westward deepening of the basin.

Outcrops in western Eagle Plain contain large exposures of convoluted interbedded sandstone and shales greater than 100m in scale, interpreted as mass-transport slope deposits. These deposits indicate the presence of a shelf-slope break in the Cretaceous basin, which contrasts with previous studies that interpret deposition in a broad, low angle shelf setting in the Canadian Foreland Basin.

Refinement of the stratigraphic framework is important for understanding regional sedimentation patterns, basin morphology, and the distribution of reservoir facies within the Cretaceous strata of Eagle Plain. Recognition of significant shelf-to-basin floor topography greatly increases the potential for large hydrocarbon reservoirs in stratigraphic traps associated with the shelf edge. Increased subsidence and accommodation at the shelf-edge allows potential space for the accumulation of thick sandstone bodies. The mass transport deposits in western Eagle Plain may represent the distal expression of a shelf-margin delta complex located farther landward at the shelf edge. Shelf-margin delta complexes are often associated with slope failures due to oversteepening of the delta front along the shelf edge. There is also potential for a turbidite fan complex basinward of the slope break by sandy gravity-driven flows. Very large oil and gas fields have been discovered in these stratigraphically confined reservoirs around the world, and could easily have been overlooked in Eagle Plain where extensive gaps in well control occur.

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.