oil

Oil, or petroleum, refers to a broad class of liquid hydrocarbons that occur in Earth’s crust. Most commonly used oil refers to crude oil, a complex mixture of hydrocarbons and other organic compounds that can be refined into fuels and chemicals. Formation: produced from ancient marine organisms buried and transformed under heat and pressure over millions of years, then trapped in reservoirs by rock.

Extraction and production: crude oil is extracted via wells drilled into reservoirs, often requiring enhanced recovery methods. After extraction, crude is transported to refineries where it is processed into products such as gasoline, diesel, jet fuel, heating oil, and feedstocks for plastics and chemicals.

Refining: primary processes include fractional distillation to separate by boiling point, followed by conversion processes such as cracking, reforming, and alkylation to improve yields of high-value fuels. Upgrades and blending adjust properties like sulfur content and octane rating.

Uses and economics: oil remains a major energy source and feedstock for the chemical industry. Global demand, prices, and supply are influenced by geopolitics, OPEC production decisions, currency exchange rates, and global economic activity. Reserves vary by definition (proved, probable, possible) and by country.

Environmental and policy context: oil extraction and use raise concerns about greenhouse gas emissions, air and water pollution, and spills. Policies often aim to improve efficiency, diversify energy, and regulate emissions. Advances include more stringent emissions standards and research into alternative energy sources and carbon capture.

History: oil has been used for lighting and lubrication since ancient times; large-scale extraction began in the 19th century, transforming transportation, industry, and geopolitics.