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Recent Developments on the Peace River Arch: Abstract
The Peace River Arch is a major tectonic interruption of the Alberta-British Columbia sedimentary basin. The Arch, as a whole, has no surface expression and its existence wasn’t suspected until uncovered by deep drilling for petroleum in the late 1940’s.
The Arch, formed in post-Cambrian time, remained positive during much of the Paleozoic and was not completely buried until early Mississippian. During Upper Devonian time, a major fringing reef complex developed around the Precambrian high and is the site of some of the earliest discoveries. In Carboniferous time, the Arch literally collapsed and about 900 m (3 000 feet) of Carboniferous sediments were deposited over the former crestal area.
Regional tilting dominated throughout Mesozoic deposition, until the Laramide orogeny produced another period of structural deformation. The unique tectonic history of the Arch produced a complex series of structural and stratigraphic traps, many of which have been successfully mapped by seismic methods. The most common structural traps are drape structures over Precambrian highs, normal faults, and Laramide folds, which are also generally associated with the older faults.
Significant hydrocarbon reserves have been discovered in Middle Devonian, Upper Devonian, Mississippian, Permian, Triassic and Cretaceous reservoirs. Ultimate recoverable reserves at the end of 1976 were about 122 × 106m3 (769 million barrels) of oil and 113 × 109m3 (4 tcf) of marketable gas. In view of the dynamic structural history, the presence of multiple reservoirs and the broad distribution of oil and gas occurrences, the Arch area should have reserves significantly larger than those found to date. The largest gas pool is Dunvegan where about 26.8 × 109m3 (950 bcf) of marketable gas is pooled in Mississippian Debolt carbonate reservoirs, separated by anhydrite interbeds. Pressure evidence and different gas water lines indicate the presence of separate reservoir compartments. An up-dip normal fault provides an effective barrier to fluid movement.
In recent years, improved seismic data gathering and processing techniques and the use of reflection amplitude, or direct hydrocarbon indicators, have resulted in the discovery of a number of new pools. Further significant discoveries can be anticipated.
Acknowledgments and Associated Footnotes
1 Westcan Oilmaps Limited, Calgary, Alberta
2 JLJ Exploration Consultants, Calgary, Alberta
3 JLJ Exploration Consultants, Calgary, Alberta
Copyright © 2009 by the Canadian Society of Petroleum Geologists