Calgary has many jobs associated with the oil industry. Read the passage below to understand where oil comes from and how it is removed from deep underground.
After scientific studies indicate the possible presence of oil, an oil company selects a well site and installs a derrick‚—a tower-like steel structure‚—to support the drilling equipment. A hole is drilled deep into the earth until oil or gas is found, or the company abandons the effort.
In rotary drilling, a rotating bit attached to a length of hollow drill pipe bores a hole in the ground by chipping and cutting rock. As the bit cuts deeper, more pipe is added. A stream of drilling “mud”‚—a mixture of clay, chemicals, and water‚—is continuously pumped through the drill pipe and through holes in the drill bit. Its purpose is to cool the drill bit, plaster the walls of the hole to prevent cave-ins, carry crushed rock to the surface, and prevent “blowouts” by equalizing pressure inside the hole.
When oil or gas is found, the drill pipe and bit are pulled from the well, and metal pipe (casing) is lowered into the hole and cemented in place. The casing’s upper end is fastened to a system of pipes and valves called a wellhead, or “Christmas Tree,” through which natural pressure forces the oil or gas into separation and storage tanks. If natural pressure is not great enough to force the oil to the surface, pumps may be used. In some cases, water, steam, or gas may be injected into the oil-producing formation to improve recovery.
Crude oil is then transported to refineries by pipeline, ship, barge, truck, or railroad.
Source: U.S. Department of Labor, Bureau of Labor Statistics. http://www.bls.gov/oco/cg/cgs005.htm
1. How is oil formed under ground? How long does it take?
2. Why is it considered a nonrenewable resource?
3. Describe how people get oil out of the ground.