Oil, also known as crude oil, is a brown-black flammable viscous liquid mined from deep underground. Mainly a mixture of alkanes, cycloalkanes and aromatics. It is a mixture formed by long-term evolution of organisms in ancient oceans or lakes, and it belongs to fossil fuels like coal. Petroleum is mainly used as fuel oil and gasoline, which constitute one of the most important primary energy sources in the world at present. The research on oil generation shows that it takes at least 2 million years to generate oil, and the oldest oil reservoir discovered today can reach 500 million years. In the long historical process of the earth's continuous evolution, there are some "special" periods, such as Paleozoic and Mesozoic. After the death of a large number of animals and plants, the organic substances that make up their bodies are constantly decomposed and mixed with sediments or carbonate sediments to form sediments. Due to the continuous accumulation and thickening of sediments, the temperature and pressure rise. With the continuous advancement of this process, sediments become sedimentary rocks and then form sedimentary basins, providing a basic geological environment for the generation of oil. With various geological processes, sediments in sedimentary basins are constantly accumulating. When the temperature and pressure reach a certain level, the organic matter of animals and plants in the sediments is transformed into carbon and oxygen compounds, and finally oil and natural gas are generated.