Oil companies obtain petroleum or crude oil by discovering oil reservoirs and establishing oil rigs. The oil rigs drill into the reservoirs and extract petroleum, which refineries process into products such as gasoline, diesel fuel, asphalt and petroleum jelly.
Crude oil, along with other naturally occurring hydrocarbons, comes from the buried remains of prehistoric organisms that underwent intense heat and pressure while mixed in sedimentary rocks. Oil companies hire geologists to find these underground supplies of oil through magnetometers, sniffers and seismic surveys. Magnetometers record fluctuations in the Earth's gravitational field that result from flowing oil. Sniffers are sensitive electronic noses that detect abnormal concentrations of hydrocarbons. Seismic surveys involve detonating explosives that create shock waves and identifying returning shock waves that reflected from petroleum-rich rock layers.
Once geologists discover oil reservoirs, oil companies prepare the location for drilling. Preparations include conducting environmental impact assessments, acquiring legal rights from the government, obtaining a water source, and determining where to dispose of rock and mud byproducts of the drilling process. The crew then sets up an oil rig system that consists of a power source, electric motors, equipment for drilling, pumps and pipes, among others.
The initial drilling tests for oil. After verifying the tests, the crew creates passages in the drilled holes where the oil can naturally flow and constructs a structure known as the Christmas tree to control the flow. Once the oil no longer flows naturally, the crew proceeds to the secondary recovery stage of extracting oil.