Open File Report 1993-23

Open File Report 1993-23

OFR 1993-23

Jurassic Boundary Study. Medicine River/Sylvan Lake (Twp. 37-40, Rg. 3-5W5)

Author(s) Strobl, R.S. Kramers, J.W. Dolby, G. Date 1993-01-01

The Medicine River/Sylvan Lake area (Townships 37-40, Ranges 3-5 W5) is one of the most prolific oil and gas areas in the Western Canada Sedimentary Basin. This area is intensely drilled and contains an abundance of subsurface data, yet in terms of correlation of the Lower Cretaceous, Jurassic and Mississippian productive intervals, it is one of the most problematic. The Jurassic units are unconformity bounded and the distinction between the Cretaceous and Jurassic strata generally cannot be made using geophysical well logs alone. Similar challenges may also be encountered in differentiating Jurassic from Mississippian strata.

The emphasis of this report is on working scale cross sections, providing a consistent set of correlations. The correlations have been reviewed by government and industry geologists with extensive experience in the area. Representative cored wells, palynology and where appropriate, petrography form the basis for correlations. The aim of this report is to provide a reference framework from which more detailed correlations and studies of the Jurassic boundary can be made. Previously, comprehensive data for this stratigraphic interval, particularly the palynology and reference sections were not publicly available to the private sector.

This report contains descriptions of key lithofacies, 21 interlocking cross sections, 102 core descriptions (with the associated core gamma or equivalent geophysical log curves), and analysis of over 200 palynology samples. Five distinct successions are investigated: the Ellerslie Formation, J-Valley units (J1 to J3), Rock Creek Member, Nordegg Member, and the Mississippian (Band Formation, Pekisko Formation, Shunda Formation and Elkton Member).