Oil and gas production
Gas and oil are produced from a petroleum field. The pressure in the reservoir that forces the material to the surface gradually declines.The pressure will decline so much that the remaining oil or gas will not get out through the porous rock to the well. When this point is reached, most of the gas in a gas field will be produced, but less than one-third of the oil in an oil field will be extracted. Part of the remaining oil can be recovered by using gas or water to push the oil to the well. But even after it, one-half the oil is usually left in the reservoir. In an effort to extract this remaining oil, oil companies are now beginning to use chemicals to push the oil to the well, or to use fire or steam in the reservoir to make the oil flow easier. New techniques that allow operators to drill horizontally and vertically, into very deep structures have dramatically reduced the cost of finding natural gas and oil supplies.
Crude oil is transported to refineries by pipelines, barges, or giant oceangoing tankers. Refineries contain a series of processing units. These units separate the different constituents of the crude oil by heating them to different temperatures. The processing units are chemically modifying them, and then blending them to make final products, principally gasoline, kerosene, diesel oil, jet fuel, home heating oil, heavy fuel oil, lubricants, and “feedstocks” fed to petrochemical plants.
Natural gas is transported, usually by pipelines, to customers who burn it for fuel or, in some cases, make petrochemicals from it. Natural gas can be liquefied at very low temperatures and transported in special ships. This method is much more costly than transporting oil by tanker. Oil and natural gas compete in a number of markets, especially in generating heat for homes, offices, factories, and industrial processes.