Oil sands are deposits of crude that are much heavier than other crude oils and consist of water, sand, mineral rich clay and bitumen. The oil sands in Alberta, Canada are considered one of the largest in the world located in Peace River, Cold Lake and Athabasca. The total area covered by these deposits is 54,400 square miles and contain approximately 1.6 trillion barrels of bitumen - of which 174 billion barrels are proven reserves and can be recovered using current technology. The vast hydrocarbon deposits of the Alberta Oil Sands creates additional, challenging problems for scientists and engineers as they seek more efficient and economical ways to recover the tar-like bitumen. Mining and in-situ are the common methods used to extract the bitumen from the oil sands, and they are discussed below.
Mining
Oil sand mining is an open pit mining technique that can be done where the mineable bitumen deposits are located near the surface of the earth. This process begins by clearing trees, draining and storing the overburden, and then removing this top layer of earth to expose the ore body. Oil sands are moved by heavy equipment such as trucks and hydraulic shovels to a special cleaning facility where the substances are mixed with hot water and caustic soda to separate the bitumen from the sand, minerals, and water. Oil sands mines in operation are located near onsite upgraders that convert the bitumen to a form of synthetic crude oil.
In-Situ
For oil sands that are too deep to support surface mining operations to an economical degree, some form of an in-situ or in-place recovery system is necessary to produce the bitumen. This method is used in approximately 80 percent of the ways that bitumen is eventually recovered. Due to the fact that bitumen will not flow under normal conditions because of its heavy viscous nature, numerous in-situ technologies have been developed that will allow easier movement and flow. In-situ oil sands production is similar to that of conventional oil production - where oil is recovered through wells. Two of the more common methods of In-Situ are listed below.
Cycle Steam Simulation- In order to soften the oil sands before pumping begins, high-pressure steam is injected into the oil sand formation for several weeks. The heat softens the oil sand and the water vapor helps in breaking up the bitumen from the sand. The pressure that has been created causes cracks to be formed that assist in moving the bitumen to producing wells. After a section of oil sands have been saturated the steam is removed and the area is allowed to sit for several weeks, soaking up the moisture and steam. The bitumen will begin to flow more freely and than can be pumped up the well to the surface, and if the production rates begin to fall the cycle steam simulation process is repeated.
Steam Assisted Gravity Drainage – This technology requires the horizontal drilling of two parallel wells through which steam is pumped into the upper well creating a high temperature chamber that serves to heat and loosen the thick bitumen. The heated bitumen is then pumped to the surface via the second horizontal well. This is one of the most popular and cost effective methods.
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