| Woodbend Group | |
| Type: | Geological group |
| Period: | Frasnian |
| Prilithology: | Limestone, dolomite |
| Otherlithology: | Shale |
| Namedby: | Imperial Oil |
| Year Ts: | 1950 |
| Region: | |
| Country: |  Canada |
| Coordinates: | 53.3451°N -113.6949°W |
| Subunits: | Cooking Lake Formation Duvernay Formation Leduc Formation Ireton Formation |
| Underlies: | Winterburn Group |
| Overlies: | Beaverhill Lake Group |
| Thickness: | up to 700m (2,300feet) |
The Woodbend Group is a stratigraphical unit of Frasnian age in the Western Canadian Sedimentary Basin.
It was first described in the British American Pyrcz No. 1 well by Imperial Oil geological staff in 1950.[1]
The Formation is composed of crystalline and dolomitized limestone (Cooking Lake Formation) in off-reef areas, bituminous shale and argillaceous limestone, detrital limestone (reef fallout), stromatoporoid calcarenite (Duvernay Formation), gray shale, argillaceous limestone, argillaceous dolomite, crystalline dolomite (Ireton Formation). In reef build-ups, it consists of massive limestone and dolomite with porosity (Leduc Formation).[2]
Oil is produced from the Leduc Formation in central Alberta since the early 1950s. Shale gas and liquids are extracted from the Duvernay Formation using horizontal drilling and multi-stage hydraulic fracturing.[3] Several project test the economic viability of extracting bitumen from the Grosmont Formation.
The Woodbend Group reaches a maximum thickness of 700m (2,300feet) in northern Alberta (where reefs were developed), and has typical thickness of 300m (1,000feet) in southern and central Alberta.[2] It extends laterally from north-eastern British Columbia through Alberta and into southern Saskatchewan and southern Manitoba. Reef build-ups range in size from small mounds to pinnacle reefs and large atoll size reefs and bank developments.
| Lithology | Max. Thickness | Reference | ||
|---|---|---|---|---|
| upper: calcareous shale and argillaceous limestone middle: fissile grey-green shale with calcirudite beds lower: massive and banded limestone with shale partings | 250-1NaN-1 | [4] | ||
| 300-1NaN-1 | [5] | |||
| 250-1NaN-1 | [6] | |||
| limestone (dolomite in the Rimbey-Meadowbrook reef trend) | 90-1NaN-1 | [7] | ||
| Lithology | Max. Thickness | Reference | ||
|---|---|---|---|---|
| 230-1NaN-1 | [8] | |||
| upper: calcareous shale and argillaceous limestone middle: fissile grey-green shale with calcirudite beds lower: massive and banded limestone with shale partings | 250-1NaN-1 | |||
| limestone | 90-1NaN-1 | |||
The Woodbend Group is conformably overlain by the Winterburn Group and conformably overlays the Beaverhill Lake Group.[2] It is transgressive in the Peace River Arch and Tathlina uplift. Newer deposits rest on the Woodbend group upon an erosional surface in eastern Alberta, south-central Saskatchewan and Manitoba.
It is equivalent to the Birdbear Formation and Duperow Formation in northern Montana, southern Saskatchewan and southwestern Manitoba, as well as parts of the Fort Simpson Formation and Muskwa Formation of northeastern British Columbia and southern Yukon, while it corresponds to the Tathlina Formation, Twin Falls Formation and Hay River Formation in the Northwest Territories.