Doig Formation

Doig Formation
Stratigraphic range: middle Anisian to Ladinian
Type Geological formation
Underlies Halfway Formation
Overlies Montney Formation
Thickness up to 190 metres (620 ft)[1]
Lithology
Primary Siltstone, Shale
Other Phosphate, Sandstone
Location
Coordinates 56°34′18″N 121°13′19″W / 56.57159°N 121.2219°W
Region NW  Alberta
NE  British Columbia
SE  Yukon
Country  Canada
Type section
Named for Doig River
Named by J.H. Armitage, 1962

The Doig Formation is a stratigraphical unit of middle Triassic age in the Western Canadian Sedimentary Basin.

It takes the name from Doig River, a tributary of the Beatton River, and was first described in the Texaco N.F.A. Buick Creek No. 7 well (located north-west of Fort St. John, east of the Alaska Highway) by J.H. Armitage in 1962. .[2]

Lithology

The Doig Formation is composed of fine grained, grey argillaceous siltstone and dark calcareous shale. [1] Nodular phosphates occur at the base of the formation. Anomalously thicker, Porous sandstone channels and bars are present locally in the upper units of the formation. [3]

Hydrocarbon production

The Doig formation is an important source rock for the Triassic Halfway and Charlie Lake formations.[4] Total organic carbon values in the "phosphate zone" at the base of the Doig are commonly greater than 4% by weight and can reach up to 11%. The "phosphate zone" is also a potential undeveloped shale gas reservoir with as much as 400 trillion cubic feet of natural gas in place. [5] Oil and gas is also extracted from the Doig Formation in conventional reservoirs along the western Montney trend and in the Peace River Arch.

Distribution

The Doig Formation reaches a maximum thickness of 190 metres (620 ft) in the Canadian Rockies foothills it thins towards the north and east. It occurs in the sub-surface in north-western Alberta, north-eastern British Columbia and southern Yukon, from 53ºN and 118ºW to the Canadian Rockies.[1]

Relationship to other units

The Doig Formation is unconformably overlain by the Halfway Formation of the Schooler Creek Group. The contact is marked by a dolomitic bed and a chert and quartz conglomerate bed.[6] Westwards it is overlain by newer Jurassic beds. It conformably overlays the Montney Formation, which rests under the phosphate pellet bed located in the base of the Doig.[1]

The formation correlates with the lower Llama Member of the Sulphur Mountain Formation in the southern ranges of the Canadian Rockies, with the Whistler Member of the Whitehorse Formation in the Muskwa Ranges, and with the Toad Formation in the upper Liard River area.

References

  1. ↑ 1.0 1.1 1.2 1.3 Lexicon of Canadian Geologic Units. "Doig Formation". Retrieved 2009-03-21.
  2. ↑ Armitage, J.H., 1962. Triassic oil and gas occurrences in northeastern British Columbia, Canada. J. Alberta Society of Petroleum Geologists, v. 10, p. 35-36.
  3. ↑ Glass, D (1997). "Lexicon of Canadian Stratigraphy" 4 (Western Canada, Including Eastern British Columbia, Alberta, Saskatchewan and Southern Alberta).
  4. ↑ Riediger, C.L. (December 1990). "Lower and Middle Triassic source rocks, thermal maturation, and oil-source rock correlations in the Peace River Embayment area, Alberta and British Columbia". Bulletin of Canadian Petroleum Geology 38 A: 218–235.
  5. ↑ Walsh, Warren (2006). "Regional “Shale Gas” Potential of the Triassic Doig and Montney Formations Northeastern British Columbia". British Columbia Geoscience Petroleum Geology Open File 2006-02.
  6. ↑ Lexicon of Canadian Geologic Units. "Halfway Formation". Retrieved 2009-03-21.