Woodbend Group

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Woodbend Group
Stratigraphic range: Frasnian
Type Geological formation
Sub-units Cooking Lake Formation
Duvernay Formation
Leduc Formation
Ireton Formation
Underlies Winterburn Group
Overlies Beaverhill Lake Group
Thickness up to 700 metres (2,300 ft)[1]
Lithology
Primary Limestone, dolomite
Other Shale
Location
Coordinates 53°20′42″N 113°41′42″W / 53.34507°N 113.6949°W / 53.34507; -113.6949 (Woodbend Group)Coordinates: 53°20′42″N 113°41′42″W / 53.34507°N 113.6949°W / 53.34507; -113.6949 (Woodbend Group)
Region  Alberta
 British Columbia
 Saskatchewan
 Manitoba
 Northwest Territories
 Yukon
Country  Canada
Type section
Named by Imperial Oil, 1950

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.[2]

Lithology[edit]

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). [1]

Hydrocarbon production[edit]

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.

Distribution[edit]

The Woodbend Group reaches a maximum thickness of 700 metres (2,300 ft) in northern Alberta (where reefs were developed), and has typical thickness of 300 metres (980 ft) in southern and central Alberta.[1] 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.

Subdivisions[edit]

Central Alberta

In central Alberta the following formations are recognized, from top to bottom:

Sub-unit Age Lithology Max.
Thickness
Reference
Ireton Formation Frasnian upper: calcareous shale and argillaceous limestone
middle: fissile grey-green shale with calcirudite beds
lower: massive and banded limestone with shale partings
250 m (820 ft) [4]
Leduc Formation Frasnian shallow water reef deposits: Stromatoporoid limestone, skeletal mudstone, boundstone, floatstone, packstone and wackestone, mostly dolomitized 300 m (980 ft) [5]
Duvernay Formation Frasnian bituminous shale, calcareous shale, argillaceous limestone with disseminated pyrite 250 m (820 ft) [6]
Cooking Lake Formation Frasnian limestone (dolomite in the Rimbey-Meadowbrook reef trend) 90 m (300 ft) [7]
Northeast Alberta

In northeast Alberta the following formations are recognized, from top to bottom:

Sub-unit Age Lithology Max.
Thickness
Reference
Grosmont Formation Frasnian limestone and dolomite, minor argillaceous dolomite, limestone, siltstone and shale 230 m (750 ft) [8]
Ireton Formation Frasnian upper: calcareous shale and argillaceous limestone
middle: fissile grey-green shale with calcirudite beds
lower: massive and banded limestone with shale partings
250 m (820 ft) [4]
Cooking Lake Formation Frasnian limestone: fossiliferous mudstone and wackestone, grainstone, stromatoporoid rudstone and floatstone 90 m (300 ft) [7]

Relationship to other units[edit]

The Woodbend Group is conformably overlain by the Winterburn Group and conformably overlays the Beaverhill Lake Group.[1] 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.

References[edit]

  1. ^ a b c d Lexicon of Canadian Geologic Units. "Woodbend Group". Retrieved 2009-03-01. 
  2. ^ Imperial Oil Limited, Geological Staff, Western Division, 1950. Devonian nomenclature in Edmonton area, Alberta, Canada. Bull. American Association of Petroleum Geologists, v. 34, p. 1807-1825
  3. ^ "The Duvernay Shale". Retrieved 2012-03-04. 
  4. ^ a b Lexicon of Canadian Geologic Units. "Ireton Formation". Retrieved 2009-12-27. 
  5. ^ Lexicon of Canadian Geologic Units. "Leduc Formation". Retrieved 2009-12-27. 
  6. ^ Lexicon of Canadian Geologic Units. "Duvernay Formation". Retrieved 2009-12-27. 
  7. ^ a b Lexicon of Canadian Geologic Units. "Cooking Lake Formation". Retrieved 2009-12-27. 
  8. ^ Lexicon of Canadian Geologic Units. "Grosmont Formation". Retrieved 2011-06-25.