Bluesky Formation

Bluesky Formation
Stratigraphic range: Lower Albian
Bluesky Sandstone
TypeGeological formation
Unit ofFort St. John Group
UnderliesWilrich Member
OverliesGething Formation
Thicknessup to 46 metres (150 ft)[1]
Lithology
PrimarySandstone
Location
Coordinates56°02′39″N 118°07′39″W / 56.0442°N 118.1274°W / 56.0442; -118.1274 (Bluesky Formation)
RegionWestern Alberta
CountryCanada
Type section
Named forBluesky, Alberta
Named byPeter C. Badgley, 1952

The Bluesky Formation is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin. It takes the name from the hamlet of Bluesky, and was first described in Shell's Bluesky No. 1 well by Badgley in 1952.[2]

Lithology and Depositional Environment

The formation is composed of mudstones, conglomerates and sandstones which can be quartzose or contain chert grains.[1] Many of the Bluesky sandstones do not display bedding features although some low and moderate-angle large scale cross-bedding has been observed in some sections.[3] The sediments were deposited in both marginally marine nearshore and fully marine offshore settings following a transgression of the ancient Moosebar Sea.[4] Bluesky sediments are separated from Gething strata by a scoured or loaded contact and occasionally by a burrowed Glossifungites surface.[3] The Bluesky Formation can be very porous and produces hydrocarbons in many areas across Western Canada.[5] Heavy oil is produced from the Bluesky formation in the Peace River area.

Distribution

The Bluesky Formation reaches a thickness of 46 meters (151 ft) in the Pouce Coupe area, and thins out toward north and west. Thin sands can be found in the Peace River area.

Relationship with other units

Although some early workers included the Bluesky Formation in the Bullhead Group, it is usually classified as the basal unit of the Fort St. John Group.[6] It is conformably overlain by the Wilrich Member of the Spirit River Formation and conformably underlain by the Gething Formation. Northeast of the town of Peace River it was deposited unconformably on Mississippian limestone. It is equivalent with the Glauconitic Sandstone of the Mannville Group in central and southern Alberta, as well as with the Wabiskaw Member of the Clearwater Formation in the eastern part of northern Alberta.

Bitumen Deposits

The Bluesky deposit of bitumen comes from the "clean estuarine reservoir sands of the Cretaceous-age Bluesky Formation" in the Peace River. Secondary production area is the Gething Formation. The combined Bluesky-Gething deposit is the primary target area for oil sands development in the Peace River area. There is a reservoir at about 600 m (2,000 ft)–700 m (2,300 ft) below the surface. Heavy oil in the Peace River, produced from bitumen deposit is extracted using wells not by mining.[7]: 9 

The oil sands of the Bluesky-Gething were deposited during the Cretaceous Period within a transgressive system, with the lower fluvial to nonmarine Gething Formation at the base and the estuarine Bluesky Formation at the top. Deposition of the Bluesky-Gething reservoir and nonreservoir units was controlled by topography of the pre-Cretaceous unconformity. The Red Earth Highlands separate the Bluesky-Gething into northeast and southwest accumulations and includes part of the Seal Lake area. In the Peace River oil sands areas, the Bluesky-Gething is overlain by the marine shales of the Wilrich Member.

— AER March 2014

References

  1. ^ a b Lexicon of Canadian Geological Units. "Bluesky Formation". Archived from the original on 2012-07-09. Retrieved 2009-02-06.
  2. ^ Badgley, Peter C., 1952. Notes on the subsurface stratigraphy and oil and gas geology of the Lower Cretaceous series in central Alberta (Report and seven figures); Geological Survey of Canada, Paper No. 52-11, 12 p.
  3. ^ a b Petrel Robertson Consulting Ltd., Canadian Discovert Ltd. (June 2011). "Deep Subsurface Aquifer Characterization in Support of Montney Tight Gas Development: Geological Report". Geoscience BC Report. 2011–11: 59.
  4. ^ Oppelt, Harold (1988). "Sedimentology and Ichnology of the Bluesky Formation in Northeastern British Columbia". In David P. James; Dale A. Leckie (eds.). Sequences, Stratigraphy, Sedimentology: Surface and Subsurface. CSPG Memoirs. Vol. 15. pp. 401–415.
  5. ^ Hayes, B.J.R. Cretaceous Mannville Group of the Western Canada Sedimentary Basin. Geological Atlas of the Western Canada Sedimentary Basin. Archived from the original on 2013-08-14.
  6. ^ Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 19: Cretaceous Mannville Group of the Western Canada Sedimentary Basin". Compiled by Mossop, G.D. and Shetsen, I. Archived from the original on 2013-08-14. Retrieved 2013-08-01.
  7. ^ "Report of Recommendations onOdours and Emissions in the Peace River Area" (PDF), AER, 31 March 2014, retrieved 23 December 2014


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