Oil (Tar) Sands

Figure 3: Sedimentary basins and major oil and gas fields of Europe, Russia ...

Figure 2: Major oil fields of the Arabian-Iranian basin region.

Heavy oil and oil sand

Oil sands (also called tar sands) consist of bitumen (soluble organic matter) and host sediment with associated minerals, excluding any related natural gas.

History of use

Discovery

In ancient times the Elamites, Chaldeans, Akkadians, and Sumerians mined shallow deposits of asphalt, or bitumen, for their own use. The Dead Sea was known as Lake Asphaltites (from which the term asphalt was derived) because of the lumps of semisolid petroleum that were washed up on its shores from underwater seeps. Centuries later, during the age of exploration, Sir Walter Raleigh found the famous "Pitch Lake" deposits in Trinidad. The Dutch made similar discoveries in Java and Sumatra.

Potential of Oil Sands as a Strategic Energy Source

Oil sands are currently found in about 70 countries around the world, including Canada, the former Soviet Union, Venezuela, Cuba, Indonesia, Brazil, Jordan, Madagascar, Trinidad, Colombia, Albania, Rumania, Spain, Portugal Nigeria, and Argentina. The United States contains scattered deposits of oil sands, mainly in Utah, Kentucky, Kansas, Missouri, Oklahoma, California, and New Mexico. Most of the oil sand deposits occur in Venezuela and Canada.

In Canada, oil sands occur in Cretaceous fluvial-estuarine deposits of northeastern Alberta, covering an area greater than140,000 kilometers2 (Figs 1A, 1B, above). Bitumen also is hosted in carbonates in Alberta but, to date, these are not commercially produced.

The largest single hydrocarbon deposit in the world is the Athabasca oil sands of northeastern Alberta, near Fort McMurray. Today these oil sands are recovered in open-pit mines by truck-and-shovel operations in which the world's largest Caterpillar 797 and 797B trucks have payloads of 380 tons. Oil sand is transported to processing plants, where hot or warm water separates the bitumen from the sand, followed by dilution with lighter hydrocarbons and upgrading to synthetic crude oil (SCO).

Syncrude Mine in the 1990s and 360-ton mechanical drive truck

About 20 percent of the oil sands reserves in Alberta are recoverable by surface mining; in-situ technologies (such as Steam Assisted Gravity Drainage, or SAGD, and Cyclic Steam Stimulation, or CSS) need to be used for the remaining 80 percent of the oil sands that are buried at depth (greater than 75 meters). In situ extraction of bitumen from deposits which are too deep for mining include much of the Athabasca deposit, and the smaller and deeper Cold Lake and Peace River deposits (see Figs. 1A, 1B).

The process of choice for in situ extraction is Steam Assisted Gravity Drainage (SAGD), in which pairs of horizontal wells are drilled near the base of the bitumen deposit. Steam is injected into the injector well which is placed about 5 metres above the producer well. The steam rises and heats the bitumen which flows down under the force of gravity to the lower producer well from which it is pumped to the surface. The bitumen is either upgraded at site, or at a regional upgrader, or mixed with diluent and shipped to a refinery. Several pilot projects have tested the SAGD process, and several commercial scale projects are currently in the construction, engineering design and regulatory approval stages.

In 2003, Alberta's reserves estimates of remaining established oil sands reserves is 174.5 billion barrels, comparable with the oil reserves of Saudi Arabia. In 2001, Alberta's production of raw bitumen and synthetic crude oil exceeded that for conventional crude oil, accounting for 53 percent of Alberta's oil production. This trend is expected to increase to be about 80 percent of Alberta's oil production by 2013.

Frances J. Hein, Chair
EMD Oil Sands Committee

EMD Members Only > Explorer Columns > November 2004