Petroleum

Required Geological Setting

Neogene and Quaternary sediments, Paleogene and older sediments

Occurrence

Oil composed of hydrocarbons containing organic sulphur and nitrogen compounds. Petroleum is contained in porous rocks such as sandstone, limestone, and tuffeceous rocks. As the density of petroleum is smaller than host rocks, it moves to the ground surface and is lost. Petroleum may be trapped in the porous reservoir rocks just below the anticline-forming cap rocks to form oil fields. Cap rocks are usually mudstone. The origin of petroleum is controversial, and there are opinions of biological origin and inorganic origin. Petroleum is classified to volatile component-rich light crude oil and volatile component-poor heavy crude oil. Light crude oil includes gasoline, kerosene, and naphtha. Heavy crude oil includes heavy oil and asphalt.