ABSTRACT

Lower Paleozoic strata in the Williston Basin comprise a basal clastic unit (Earlie, Deadwood and Winnipeg formations) and an upper sequence of carbonates and minor evaporites (Red River, Stony Mountain, Stonewall and Interlake formations). To date in Saskatchewan, only the Ordovician Red River Formation has produced economic quantities of hydrocarbons. In contrast, all these Lower Paleozoic formations, are productive in the adjacent portion of the Williston Basin in Montana and North Dakota. Notably, only 254 wells penetrate Ordovician strata in the southern one-third of Saskatchewan (Tp 1 to 25). Analysis of the distribution of source and reservoir rocks, oil generation and migration history, basement structures and hydrocarbon shows indicates that significant Lower Paleozoic oil reserves remain undiscovered in Saskatchewan.

Sixteen wells, including two drilled horizontally, have produced (to October, 1994) approximately 1.2 x 106 bbls (0.2 x 106m3) of oil from Red River strata in Saskatchewan. Kukersites in the lower Red River (Yeoman) are the source for this oil. Productive wells, with the exception of Aldon Weir Hill 9-29-6-6W2, are located within or immediately adjacent to the Saskatchewan part of the source rock sub-basin (Rge 9 to 21W2). Hydrocarbon prospects in Lower Paleozoic strata within this region and to the east are enhanced by recent studies (Burrus et al., this volume) which indicate that generation and migration of Red River-sourced oil occurred before growth of the Nesson anticline as a potential barrier to updip migration of large volumes of oil from the more thermally mature areas of North Dakota and Montana. The recovery of 90 ft (27.4 m) of oil, 100 ft (30.5 m) of oil-cut mud and 120 ft (36.6 m) of water in a drillstem test of the Interlake Formation at the MOWS N Redvers 14-19-8-32W1 well indicates petroleum potential in an area having few penetrations of Silurian or Ordovician strata.

Exploration of the hydrocarbon potential of Lower Paleozoic rocks in southern Saskatchewan will likely increase when undeveloped deep rights revert to the Crown in April, 1998.