ABSTRACT

In west-central Saskatchewan the Sparky and General Petroleums (G.P.) "members" of the Lower Albian Upper Mannville Group include several sequences of shales and sands capped by coal. Mobil's successful horizontal wells in the Celtic Field were completed using SAGD (Steam Assisted Gravity Drainage) production technology that necessitated a rigorous examination of reservoir geometry. Some exploration and development models include the assumption that Upper Mannville valley-fill resulted from meandering rivers. This analysis has resulted in the recognition of linear and arcuate sand and shale depositional patterns in the valley-fill in the northwest part of the Celtic Field, at least some of which are probably estuarine.

The Sparky and General Petroleums members in the Celtic Field comprise "regional" clastics and valley-fill sediments. The regional strata are deeply dissected in two places: in the centre of the field by a narrow channel and in the northwest of the field by a parallel, broader valley. The northwestern sand bodies are linear or arcuate in form and parallel or sub-parallel to the valley margins. Some appear as small clinoforms and others resemble longitudinal bars in an estuary. The thicker sand bodies are up to 600 m wide and more than 2 km long. Prairie Evaporite dissolution produced collapse features clearly defined on the karstic Duperow surface before and during Mannville deposition but had little influence on the G.P. and Sparky sand and shale orientation.