Abstract

By the end of 1969, a total of 10.7 billion barrels of recoverable oil and 55 trillion cubic feet of recoverable gas had been discovered in Alberta. Average daily production was 966,388 barrels of oil and 4.6 billion cubic feet of gas and the average drilling density was one exploratory well per 21 square miles. The sedimentary section increases in thickness from zero feet at the edge of the Precambrian Shield on the northeast to 19,000 feet in front of the Foothills and then thickens abruptly southwestward into the Cordillera. The Paleozoic sedimentary pattern was set by transgression from the northwest which deposited overstepping facies of marine sediments leaving open sea marine shales to the northwest, shelf carbonates to the southeast and evaporites behind the shelf area farther to the southeast. Mesozoic sedimentation consisted mainly of sands from uplifted Cordilleran sources transported eastward and intercalated with marine shales across the Alberta shelf. General uplift climaxed in the Eocene with the Laramide orogeny and was followed by Pleistocene glaciation. The total volume of sediments in the Plains and Foothills is 333,400 cubic miles of which 24 per cent is sandstone, 49 per cent shale, 21 per cent carbonate, and 6 per cent evaporite. Upper Devonian rocks contain 43.8 per cent of the Province’s proven hydrocarbons followed by the Carboniferous with 14.8 per cent, the Upper Cretaceous with 14.8 per cent, the Upper Cretaceous with 14.1 per cent, the Lower Cretaceous with 14 per cent, the Middle Devonian with 9.5 per cent and the Jurassic and Triassic with 0.8 per cent and 0.5 per cent, respectively.

Permian and Tertiary rocks contain minor amounts of gas but have limited potential because of their continental facies. Cambrian and Ordovician sediments have no proven reserves but the Cambrian, because of its attractive marine facies, may have some hydrocarbon possibilities. On the basis of theoretical ultimate recovery per cubic mile of total sediments, an “Estimated Range of Ultimate Recoverable Hydrocarbons” has been established which gives a range of 14 to 19 billion barrels for oil and 70 to 99 trillion cubic feet for gas. The mean figures for these ranges are 16 billion barrels of oil and 84 trillion cubic feet of gas.