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Oil Sands Tapped as Major Resource

Field Trip Planned at Calgary Meeting

Oil sands consist of bitumen (soluble organic matter) and host sediment with associated minerals, excluding any related natural gas. Most of the oil sand deposits in the world are found in Venezuela and Canada.

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

In 2003, Alberta's reserves estimates of remaining established oil 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.

Development of the Canadian oil sands industry has a history of over 90 years. In 1913 Sidney Ells organized the first field parties to work on oil sands, hauling out over nine tons of oil sands by scows up the Athabasca River valley (figure 2).

Today, near Fort McMurray, 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) — a mixture of pentanes and heavier hydrocarbons.

Image Caption

Figure 1
Location of the Alberta oil sands in Canada: (A) regulatory areas of oil sands development; (B) surficial expression of the Athabasca, Peace River and Cold Lake deposits.

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Oil sands consist of bitumen (soluble organic matter) and host sediment with associated minerals, excluding any related natural gas. Most of the oil sand deposits in the world are found in Venezuela and Canada.

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

In 2003, Alberta's reserves estimates of remaining established oil 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.

Development of the Canadian oil sands industry has a history of over 90 years. In 1913 Sidney Ells organized the first field parties to work on oil sands, hauling out over nine tons of oil sands by scows up the Athabasca River valley (figure 2).

Today, near Fort McMurray, 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) — a mixture of pentanes and heavier hydrocarbons.

(An EMD-sponsored field trip at the 2005 AAPG Annual Convention in Calgary will visit the McMurray oil sands in the Athabasca area.)

About 20 percent of the oil sands reserves in Alberta are recoverable by surface mining; in-situ technologies need to be used for the remaining 80 percent of the oil sands that are buried at depth (greater than 75 meters).

Alberta's oil sands are unconsolidated, held together by the pore-filling bitumen. The bitumen is a natural, tar-like mixture of hydrocarbons that when heated has a consistency of molasses.

In its natural state, bitumen (density range of 8-12° API; at room temperature viscosity greater than 50,000 centipoises) will not flow to a well bore.

In Alberta other heavy oil in sand is also considered as "oil sands" if it is located within the oil-sand application areas (figure 1A). However, because the pore-fluid is heavy oil and will flow to a well, these deposits are referred to as "primary in-situ crude bitumen." The major challenge of recovering bitumen from depth is to overcome its high viscosity to allow it to flow to the well bore.

To do this, thermal (or other non-primary) in-situ methods are used — most commonly Cyclic Steam Stimulation (CSS) and Steam Assisted Gravity Drainage (SAGD).

Canada's largest in-situ bitumen recovery project uses CSS at Cold Lake. Steam injected down the well bore into the reservoir heats the bitumen; followed by a soak period; and then the same well bore is used to pump up fluids (figure 3A).

At Cold Lake about 3,200 wells are currently operating from multiple pads, with two aboveground pipelines — one to deliver steam and the other to transport fluids back to the processing plant.

At Athabasca, the SAGD technology is used.

Horizontal well pairs (700 meters long with five-meter vertical separation) are drilled from surface pads to intersect bitumen pay (figure 3B). Steam from the upper injector well expands, reducing the viscosity of the bitumen, allowing the bitumen to flow. A shell forms at the cold interface with the unheated reservoir, along which bitumen/condensate drain by gravity to the lower producing well (figure 3B).

Electrical submersible pumps (ESPs) may assist in lift.


Continuing challenges for economic in-situ recovery involve water and gas requirements for steam generation, reclamation and emission controls of greenhouse gases. Generally, it takes 28 meters3 (1,000 feet3) of natural gas and from 2.5 to four barrels of water to produce one barrel of bitumen. Reclamation of mining sites is done to a standard to at least the equivalent of their previous biological productivity.

Beginning in the mid-1970s, the North American energy crises have made the Canadian oil sands a more strategic resource for North American energy needs, accelerating industry's interest and efforts to tap these vast bitumen reserves.

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