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Alberta Online Encyclopedia
Canadian Petroleum Heritage
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Oil

BitumenFor years, most wells were drilled vertically. Today, technology has allowed for wells to be drilled directionally or horizontally to intersect more of the producing reservoir. However, crude oil extraction involves more than drilling and pumping. Unlike natural gas reservoirs, oil does not contain enough pressure to gush to the surface, but has to be displaced from a porous formation to the wellbore. The success of a well depends on making a strong connection between the wellbore and the reservoir system. Planning before the drilling starts is vital.

When the crude oil is in the wellbore, it can be pumped up to the surface. The most common method uses a pump lowered down the wellbore on a string of rods, and operated by an up and down motion created by a pumpjack at the surface. Other pumps use a rotary motion. This method can recover up to 60 percent of the recoverable oil in a reservoir. Other recovery methods involve injecting water or natural gas to maintain reservoir pressure. This is necessary because the pressure drops as the resource is produced. For heavy oil, steam is used to soften the bitumen, or to enlarge or create channels and cracks for the oil to flow more freely. The two most successful methods are cyclic steam stimulation and steam-assisted gravity drainage.

Steam Assisted Gravity Drainage (SAGD) is a method that uses heat for recovering heavy oil. The process utilizes twin horizontal wells drilled and extended into the base of a reservoir with a horizontal steam injector placed directly above the horizontal production well. The mobilized oil drains by gravity to the lower well and comes to the surface. The Alberta Research Council’s Dr. Tawfik Nasr is working on the continued development of SAGD.

 

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