The oil-forming mechanism of petroleum has two theories: biological deposition and petrochemical oil. The former is widely accepted that oil is formed by the long evolution of organisms in ancient oceans or lakes, which belongs to the oil deposited by organisms and cannot be regenerated. The latter thinks that oil is generated by carbon in the earth's crust, which has nothing to do with living things and is renewable.

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The nature of petroleum varies from place of origin, with a density of 0.8-1.0g/cm3, a wide range of viscosity, a great difference in freezing point (30-60 degrees Celsius), and a boiling point ranging from normal temperature to over 500 degrees Celsius. It is soluble in various organic solvents and insoluble in water, but can form an emulsion with water. But the composition and appearance of oil in different oil fields can be very different. Petroleum is mainly used as fuel oil and gasoline, which constitutes one of the most important secondary energy sources in the world. Petroleum is also the raw material of many chemical industrial products, such as solvents, fertilizers, pesticides and plastics. 88% of the oil produced by 20 12 is used as fuel, and the other 12% is used as chemical raw materials. In fact, oil is a non-renewable raw material.