Overview

The  Ordovician Bighorn Group contains the geologically oldest established production in southern Saskatchewan from established fields in Lake Alma and West Oungre.  Production from the Ordovician of the US portion of the Williston Basin is far more significant with Red River (Yoeman Formation equivalent) reservoirs comprising major exploration targets.  Previously in the Williston Basin, hydrocarbon sourcing and reservoiring was considered to be intra-stratal, so it was critical to assess thickness, richness and areal extent of potential source intervals.  However, with more geochemical investigations available evidence of cross-stratal migration is more apparent, and the mapping of mature, rich source rocks in the Ordovician section has implications for prospects within the Bighorn Group and younger superjacent sediments.

The Yeoman Formation succession of the Big Horn Group, of the Williston Basin, contains significant oil and gas reserves, apparently derived from an indigenous Ordovician source rock.  Two main source intervals are postulated; the underlying Winnipeg shale and interbedded kerogenite layers within the Yoeman Formation.  This study addresses the nature and distribution of these kerogenite layers and provides a model of source rock distribution and maturation critical to the evaluation of this locally-sourced play type.

The study area is located in southeastern Saskatchewan from Township 1 to 10 between Ranges 5W2 and 30W2.  At the time of the study 182 wells penetrated the Yoeman Formation.  Cored intervals from 21 wells were described in detail and cored intervals from an additional 27 wells were reviewed.  In total 64 samples were taken for geochemical analysis.

Click globe for map of study area.

• fully illustrated text (62 pages plus 8 colour plates) documenting stratigraphy, depositional setting, hydrocarbon source rock distribution, maturation & migration, core descriptions, and database;
• 3 regional cross sections;
• 12 stratigraphic intervals picks from Top Stonewall Formation to Top Winnipeg Formation;
• 182 well database available in hardcopy and digital formats;
• core descriptions from 21 wells with internally consistent correlations;
• geochemical analyses for 64 samples.