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Oil Sands

Oil sandsOil sands are mixtures of sand, water, clay, and crude bitumen. Oil sand grains have layers of water surrounding a grain of sand, and a film of bitumen surrounding the water. The extraction process involves removing the sand from the crude oil. This is not an easy process. As early as the 1860s, hard, tight oil sands were being shot with gunpowder and then nitroglycerin to shatter the rock at the bottom of the wellbore. The practice of shooting explosives increased flow but was temporary, as it destroyed the well and was dangerous. The more popular and safer method was open pit mining. Mine equipment from the early years was scaled up significantly when large commercial operations started to develop. The first large scale commercial operation, Great Canadian Oil Sands (Suncor Energy), introduced bucketwheels from the coal mining industry when they opened in 1967.

Syncrude Canada Limited opened in 1978 and introduced gigantic draglines sixty times as large as the bucketwheels. However, the use of draglines and bucketwheel re-claimers in the mining process is being phased out, because about 80 percent of the oil sands in Alberta are buried too deep below the surface for open pit mining. This oil must be recovered by in situ techniques. The phrase, "in situ" is Latin for "in place." Using drilling technology, steam is injected into the deposit to heat the oil sand thereby lowering the viscosity of the bitumen. The hot bitumen migrates towards the producing wells, which, in turn, brings the oil to the surface while the sand is left in place. Steam Assisted Gravity Drainage (SAGD) is a type of in situ technology that uses innovation in horizontal drilling to produce bitumen. Two parallel horizontal wells are drilled through the oil sand deposit. Steam is then injected into the top well and loosens the crude oil from the sand. The oil flows to the lower well where it is pumped to the surface. The technology is expensive and requires certain conditions like a nearby water source. However, due to the high oil recovery rates, SAGD is the most popular enhanced oil recovery system used in Canada.

There are other in situ ways of recovering oil sands. Cyclic Steam Stimulation (CSS) injects high pressure and high temperature steam into the sand deposits. The pressure and heat separate the sand and bitumen, where the bitumen flows to a producing well and is pumped to the surface. The Vapour Extraction Process (VAPEX) is similar to SAGD, but uses solvents such as ethane or propane, which creates a vapour chamber that the oil flows through with the help of gravity.

 

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