ABSTRACT: Sub-Devonian Petroleum Systems and Plays in Williston Basin

OSADETZ, KIRK G., LLOYD R. SNOWDON, and PAUL. W. BROOKS, Institute of Sedimentary and Petroleum Geology, Calgary, Alberta, Canada

Five oil families occur in Williston basin sub-Devonian reservoirs. Most significant are oils from Middle and Upper Ordovician kukersites, Type I source rocks, that supply Upper Ordovician and Silurian pools of Cedar Creek Anticline, northeast Richland County Red River pools, and structures in Sheridan County and southeastern Saskatchewan. Middle Ordovician Winnipeg Formation Type II source rocks are the probable source of minor oil production from that formation. Sources for oil families occurring in Newporte field and as stains and subeconomic shows in southern Saskatchewan are not yet identified. A fifth family, sourced by the Middle Devonian Winnipegosis Formation, forms Silurian pools on Nesson Anticline owing to up-structure, down-strata migration through faults on the Anticline s western flank. Among sub-Devonian sourced oils, only those from kukersites have a substantial established reserve and a well-characterized source rock. The absence of these oils from the Williston basin's eastern flank indicates significant undiscovered potential.

Compositional peculiarities and thermal history of this source rock suggest intense hydrocarbon generation occurred before the Nesson Anticline was an effective trap. Oils expelled from kukersites toward the eastern flank were probably entrapped in stratigraphic and diagenetic plays associated with structurally influenced lithofacies trends along the long. 102 degrees W. Sources for other oil systems are too poorly understood to speculate on their undiscovered potential but should not be discounted by explorationists.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)