So-called tar or heavy oil sands are those hydrocarbon deposits which are too viscous to permit recovery by natural flowage into wells. The best known of such deposits are the Athabasca tar sands near Fort McMurray in northeastern Alberta, Canada, and two smaller deposits, al­so in northern Alberta. The Athabasca deposit has an area of about 9,000 square miles and represents about 88 per cent of the total (Pow, Fair­banks, & Zamora, 1963). These occur at depths ranging from 0 at surface outcrops to 2,000 feet. The total producible oil reserves represented by these three deposits amounts to about 300 billion barrels.

Unsuccessful small-scale attempts to extract these deposits have been made repeatedly during the last half century. Large-scale develop­ment work was begun by major oil companies about 15 years ago, and the first successful operation was begun by a combination of oil companies about 1966. Further development will undoubtedly occur as soon as a prospective shortage of oil from conventional sources becomes evident. When the magnitude of these deposits is compared with the figures for the United States, their significance as a major source of liquid fuels becomes evident.