In some cases, natural gas is extracted along with oil. Oftentimes this gas is separated from the oil and injected back into the production well to maintain pressure and the flow of oil. Eventually, however, the pressure drops to a point where the flow of oil stops. The water washes some of the remaining oil out of the rock, pushing it through the reservoir and out the production well. The extracted crude oil is then pumped through a network of pipelines, and via barges, to petroleum refineries across the country.
Gasoline represents over half of all products generated by oil refineries in the United States.
The Environmental Defense Community Guide to Oil Refining explains the primary processes of a refining facility and available pollution prevention options. Natural Gas Natural gas is extracted from the earth through wells, much like crude oil. Wells drilled into the earth, hundreds or thousands of feet deep, tap reservoirs of this fossil fuel resource. Like crude oil, natural gas flows freely through the well, from the reservoir to the surface, due to natural pressure. These wells only require a series of pipes and valves at the surface to control the flow of gas.