Alberta basin
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Introduction
Alberta Basin, large, petroleum-rich sedimentary basin along the eastern edge of the Rocky Mountains in western Canada. It extends from British Columbia through Alberta and Saskatchewan into Manitoba. The basin was formed when the Earth’s crust sank along the continental side of the Rocky Mountains during the Devonian Period (about 415 to 360 million years ago).From that time until the Late Cretaceous Period (about 100 to 65 million years ago), the region was covered by the sea at various intervals. Marine sediments gradually accumulated in the deepest parts of the basin, and large reefs composed of marine fossils and algae formed along its margins.
History
the Alberta basin is a part of the greater Western Canada Sedimentary Basin (WCSB) it is a vast sedimentary basin underlying 1,400,000 square kilometres (540,000 sq mi) of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock extending from the Rocky Mountains in the west to the Canadian Shield in the east. This wedge is about 6 kilometres (3.7 mi) thick under the Rocky Mountains but thins to zero at its eastern margins. The WCSB contains one of the world's largest reserves of petroleum and natural gas and supplies much of the North American market, producing more than 16,000,000,000 cubic feet (450,000,000 m3) per day of gas in 2000. It also has huge reserves of coal. Of the provinces and territories within the WCSB, Alberta has most of the oil and gas reserves and almost all of the oil sands.
Petroleum elements
Source rocks
The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.
Migration
Through vertical migration the main component of maturity of most Phanerozoic strata occurred during deep burial under Upper Cretaceous and/or Paleogene molasse in foredeeps developed in response to crustal loading during the easterly migration of the foreland fold and thrust belt.
Seals and traps
Each facies belt and each assemblage have a unique set of traps and plays controlled by the types of rocks available as reservoirs and seals. Deposits within the facies belts that make up the assemblages are composed typically of stacked progradational sequences that are commonly punctuated by either transgressive or erosional events.
Production
Oil sands
According to the Alberta Energy and Utilities Board (EUB, now known as the Alberta Energy Regulator, the AER), Alberta's oil sands areas contain an ultimately recoverable crude bitumen resource of 50 billion cubic metres (315 billion barrels), with remaining established reserves of almost 28 billion cubic metres (174 billion barrels) at year-end 2004. The Athabasca Oil Sands, the Cold Lake Oil Sands and the Peace River Oil Sands, which contain initial oil-in-place reserves of 260 billion cubic metres (1.6 trillion barrels), an amount comparable to the total world reserves of conventional oil. The World Energy Council reported (2007) that the three Alberta oil sands areas contain at least two-thirds of the world's discovered bitumen in place. These three major oil sands areas, all in Alberta, have reserves that dwarf those of the conventional oil fields. By 2007 the Alberta natural bitumen deposits were the source of over one third of the crude oil produced in Canada.
Natural gas
Canada is the third largest producer and second largest exporter of gas in the world, with the vast majority of it coming from the Alberta basin. The Alberta basin is estimated to have 143 trillion cubic feet (4,000 km3) of marketable gas remaining (discovered and
undiscovered), which represents about two thirds of Canadian gas reserves. Over half of the gas produced is exported to the United States. However, Canadian gas reserves represent less than one percent of world reserves and are rapidly becoming exhausted.
Coal
The Alberta basin contains about 90 percent of Canada's usable coal resources.[11] Their rank ranges from lignite to semianthracite. About 36 percent of the total estimated 71,000 megatonnes of usable coal is bituminous, including a high proportion of medium to low volatile coals. The low sulfur content and acceptable ash levels of these bituminous coals make them attractive as coking feedstocks, and large quantities are mined for that purpose. However, the lack of heavy industry in Western Canada means that only a limited amount of this coal is consumed in Canada, and most is exported to Japan, Korea and other countries.
References
<ref>[Alberta Basin. (n.d.). Retrieved November 16, 2020, from https://www.britannica.com/place/Alberta-Basin]<ref>.
Bachu, S. (1999, December 01). Flow systems in the Alberta Basin: Patterns, types and driving mechanisms. Retrieved November 16, 2020, from https://pubs.geoscienceworld.org/cspg/bcpg/article-abstract/47/4/455/57766/Flow-systems-in-the-Alberta-Basin-Patterns-types?redirectedFrom=PDF
Berbesi, L., Primio, R., Anka, Z., Horsfield, B., & Higley, D. (2012, August 01). Source rock contributions to the Lower Cretaceous heavy oil accumulations in Alberta: A basin modeling study. Retrieved November 16, 2020, from https://pubs.er.usgs.gov/publication/70005736
Bustin, R. (2003, April 08). Organic maturity in the western Canada sedimentary basin. Retrieved November 16, 2020, from https://www.sciencedirect.com/science/article/abs/pii/016651629190026F
Chapter 1 - Introduction. (2020, September 13). Retrieved November 16, 2020, from https://ags.aer.ca/reports/chapter-1-introduction
Chapter 31 - Petroleum Generation and Migration. (2020, September 13). Retrieved November 16, 2020, from https://ags.aer.ca/reports/chapter-31-petroleum-generation-and-migration
Figure 1: Geology of the Alberta Basin and study regions (blue = Saline Aquifer Mapping area in deeper basin; red= shallower basin area: geological map modified from from Mossop and Shetsen, 1994).
Figure 2:Headwaters. (2020, July 22). Retrieved December 14, 2020, from https://albertawilderness.ca/issues/wildwater/headwaters/