Most of the countries with the highest oil reserves have been covered by large-scale oceans in the last 200 million years, and oil and gas mainly produce strata formed from ancient oceans.

Take Saudi Arabia as an example. During the Jurassic period 65.438+0.9 billion years ago, its territory was still in the warm shallow sea near the tropics, and it continued until the Cretaceous period. Zooplankton is endless, and the battle in the ocean is all-weather. Countless organic matter accumulated on the seabed, which gave birth to a series of source rocks and eventually formed rich oil.

The difference between oil and crude oil:

Petroleum is an industrial term, but relative to mineral resources, petroleum industry is a mineral resources industry. In the process of oil exploration, according to the degree of exploration and proven situation, the oil reserves are calculated and determined. Oil reserves are the results of geological exploration and a kind of original mineral resources to be developed.

Crude oil is the oil that is buried in the rock and mined. It maintains its original physical and chemical form, is the primary product of petroleum industry, and its use value is the result of oilfield development. Crude oil export is a developed mineral resource export.

The word petroleum is often used to describe the permeability, porosity and reservoir grade of oil layers. The term "crude oil" is mostly used in the national statistics of crude oil production statistics, the evaluation of crude oil physical and chemical properties, and the description of recovery ratio, recovery degree and oil recovery rate.

As a mineral resource, oil refers to oil containing water and gas, while crude oil is an industrial product, in which water and gas have been separated from oil, which is a qualified industrial product.