Hairuo Qing¹, Fran Haidl², Donald Kent³, Kim Kreis²

(1) University of Regina, S4S 0A2 Regina, SK
(2) Saskatchewan Energy and Mines, Regina, SK
(3) D.M. Kent Consulting Geologist Ltd, Regina, SK

ABSTRACT: Ordovician Hydrocarbon Reservoirs in Red River Strata (Yeoman and Herald Formations), Northern Williston Basin, Southeastern Saskatchewan

The discovery in December 1995 of prolific Red River reservoirs below producing Mississippian strata in the Midale area of southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. Cumulative oil production reached 2.29 x 106 m3 (14.4 x 106 bbls) in June 2000, primarily from the upper part of the Yeoman Formation (C Burrowed Mbr). The lower part of the Lake Alma Member of the Herald Formation (C Laminated Mbr) has also yielded hydrocarbons.

The Yeoman Formation is characterized by burrow-mottled (Thalassinoides) packstones, wackestones, and mudstones that have been subjected to a variable degree of dolomitization which is interpreted to have occurred in several stages. Lake Alma reservoirs consist of porous medium crystalline dolostones while non-reservoir rock is generally composed of laminated and thinly bedded, fine crystalline dolomudstones.

Recent studies by GSC scientists indicate that hydrocarbons in Red River pools are sourced from kukersitic beds within the Yeoman. The wide range of API values (26o to 42o) reflects: 1) lower maturity oil locally sourced from disseminated G. prisca material; 2) migrated higher maturity oil derived from G. prisca kukersites deeper in the basin; or 3) a mixture of these two types. Most of these pools are small fault-bounded traps that are spatially related to Precambrian basement highs which sometimes show evidence of reactivation during the Phanerozoic.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado