Crude oil, petroleum, condensate

Crude oil (Crude oil), also known as "black gold", is a liquid or semi-solid flammable substance, and coal, natural gas is a non-renewable fossil fuel, is one of the world's important primary energy. It is composed of a very complex mixture of different hydrocarbons, mainly consisting of oil (hydrocarbons), asphaltene (dark brown or black brittle solid matter), gum, and carbon (a non-hydrocarbon).

The physical properties of crude oil vary from place to place, from reservoir to reservoir, and there is no fixed chemical composition and therefore no fixed physical constant. Generally speaking, the density of crude oil is 0.8~1.0g/cm3, the viscosity range is very wide, the freezing point difference is also very large (-60℃~32℃), the boiling point range is above 500℃ at normal temperature, soluble in a variety of organic solvents, insoluble in water, but can form a emulsion with water.

The chemical elements that make up crude oil, mainly a variety of hydrocarbons composed of carbon and hydrogen. The proportion of carbon in crude oil is 83% to 87%, hydrogen is 11% to 14%, the rest is sulfur (0.06% to 0.8%), nitrogen (0.02% to 1.7%), oxygen (0.08% to 1.82%), trace non-metallic elements (phosphorus, chlorine, iodine, etc.) and trace metal elements (nickel, vanadium, iron, antimony) and other impurities.

Although the basic elements of the composition of crude oil are similar, there are many varieties of crude oil produced in different places and different strata. In the crude oil of different origin, the structure and proportion of various hydrocarbons vary greatly, of which the three major hydrocarbons of straight chain alkane, cycloalkane and aromatic hydrocarbon are the main components, usually the proportion of more than 90%. However, the content of different hydrocarbons often varies greatly, and non-hydrocarbon compounds, that is, compounds containing sulfur, nitrogen and oxygen, account for very little of the composition. When crude oil is extracted, it also contains metal salts, mainly a mixture of sodium, calcium, magnesium and other chlorides, with a salt content of 0.02% to 0.055%, so crude oil needs to be dehydrated and desalted after being extracted from the ground to be processed.

Crude oil is a heterogeneous commodity, the quality of crude oil in different places is often very different, so crude oil is difficult to be standardized like metals and other industrial products, and the characteristics of crude oil quality diversification is also reflected in crude oil production, trade, processing and pricing and other links.

Color of oil

In people's first impression, crude oil is black, but in fact known as "black gold" of the crude oil color is very rich, red, golden, dark green, black, brown red and even transparent, the color of crude oil is its own gum, asphaltene content reflected, usually the lighter the color of crude oil, indicating that the lower the content of gum, asphaltene, the smaller the density, containing low boiling point components of the higher. Some parts of the world even have colorless crude oil output, some Wells in Chongqing Huangguashan and North China Dagang oil fields produce colorless oil, Karamay oil is brown to black, Daqing, Shengli, Yumen oil are black. Colorless oil is produced in California, Baku, Romania, and Sumatra, Indonesia. The formation of colorless petroleum may be related to the adsorption of colloid and asphaltene by rocks during migration. However, different degrees of dark oil account for the absolute majority, almost distributed in the world's major oil and gas basins.

What is the difference between crude oil and petroleum?

People used to equate oil with crude oil, in fact, this is not a rigorous statement, in 1983, the 11th World Petroleum Congress officially defined oil and other terms:

Petroleum: A mixture of gaseous, liquid and solid hydrocarbons that occur naturally.

Crude Oil: One of the basic types of petroleum that is stored in underground reservoirs as a liquid at atmospheric pressure and includes some liquid non-hydrocarbon components. Generally speaking, the viscosity of crude oil in the reservoir state does not exceed 10mPa·s.

Natural Gas: One of the basic types of petroleum, gaseous under formation conditions or dissolved in crude oil, gas after extraction at normal temperature and pressure. Natural gas may also contain a small amount of non-hydrocarbon components.

Natural Gas Liquids: Portions of natural gas recovered as liquid in a natural gas processing unit, consisting primarily of natural gas gasoline and condensate and possibly containing small amounts of C1 to C4 alkanes and non-hydrocarbon components.

Natural Tar: refers to petroleum deposits, which are semi-solid or solid, such as Canadian oil sands, with a viscosity greater than 10mPa·s at normal temperature and pressure, and often contain a small amount of sulfur, nitrogen, oxygen, and metallic non-hydrocarbon substances.

Although the definition of oil and crude oil is unified at the industry level, there are still some differences in the definition of countries, the key issue is whether natural gas liquids and condensate (oilfield associated) and oil flows extracted from natural tar and bitumen meet the definition of crude oil. Natural gas condensates are not currently covered by mainstream official bodies such as the International Energy Agency (IEA) and the Organization of Petroleum Exporting Countries (OPEC), and should be excluded as long as condensates can be separated from industrial oil streams. However, the U.S. Energy Information Administration (EIA) also classifies condensate extracted from some mines as crude oil in its definition.

What is condensate?

Condensate oil refers to the liquid phase component from the condensate gas field or oil field associated with natural gas condensate, also known as natural gasoline. The characteristic of condensate oil is that it exists in a gas phase underground, called condensate gas, and it is liquid after it is produced to the surface of the pool. Its main component is a mixture of C5~C7 hydrocarbons, and contains a small amount of hydrocarbons and sulfides greater than C8 impurities, its fraction is more than 20℃~200℃, good volatility. Condensate can be used directly as fuel and is also a high-quality raw material for the refining industry, usually the yield of naphtha is 60% to 80%, the yield of diesel is 20% to 40%, the API value is above 50 degrees, and the boundary between it and ultra-light crude oil is not obvious.