What are the properties of crude oil

If you want to know a variety, you should not only know a part of it, but also learn more. Let's talk about the properties of crude oil.

The properties of crude oil include physical properties and chemical properties. Physical properties include color, density, viscosity, freezing point, solubility, calorific value, fluorescence, optical activity, etc.; chemical properties include chemical composition, component composition and impurity content.
physical property
Generally, the relative density of crude oil is between 0.75-0.95, a few of which are greater than 0.95 or less than 0.75, and those with relative density of 0.9-1.0 are called heavy crude oil, and those less than 0.9 are called light crude oil.
Crude oil viscosity refers to the internal friction resistance caused by crude oil flowing. The viscosity of crude oil depends on temperature, pressure, dissolved gas volume and its chemical composition. The viscosity decreases with the increase of temperature, increases with the increase of pressure, decreases with the increase of dissolved gas volume, and decreases with the increase of light oil components. The viscosity of crude oil varies greatly, generally between 1-100MPa · s. The crude oil with high viscosity is commonly known as heavy oil, and the development difficulty of heavy oil is increased due to poor liquidity. Generally speaking, crude oil with high viscosity has higher density.
The temperature at which crude oil cools to a solid from liquid is called freezing point. The freezing point of crude oil is about - 50 ℃ - 35 ℃. The freezing point is related to the component content in petroleum. The content of light component is high, the freezing point is low, and the content of heavy component is high, especially the content of paraffin is high.
chemical property
Crude oil is a mixture of alkanes, cycloalkanes, aromatic hydrocarbons and alkenes. The main components are carbon and hydrogen, accounting for 83-87% and 11-14% respectively; there are also a small amount of sulfur, oxygen, nitrogen and trace phosphorus, arsenic, potassium, sodium, calcium, magnesium, nickel, iron, vanadium and other elements.
Wax content refers to the percentage of paraffin and paraffin in crude oil under normal temperature and pressure. Paraffin is a white or light yellow solid, composed of higher alkanes, melting point of 37 ℃ - 76 ℃. Paraffin is dissolved in oil as colloid in the underground, and can be separated out from the oil when the pressure and temperature decrease. The temperature at which paraffin begins to crystallize in formation crude oil is called wax precipitation temperature. The higher the wax content, the higher the wax precipitation temperature.
The high temperature of wax precipitation makes the oil well easy to form wax, which is unfavorable to oil well management.
Sulfur content refers to the percentage of sulfur (sulfide or elemental sulfur) in crude oil. The sulfur content in crude oil is small, generally less than 1%, but it has great influence on the properties of crude oil, corrodes pipelines and is harmful to human health. According to the different sulfur content, it can be divided into low sulfur or sulfur-containing oil.
Gum content refers to the percentage of gum contained in crude oil. The gel content of crude oil is generally between 5% and 20%. Colloid is a kind of polycyclic aromatic hydrocarbon compounds with large molecular weight (300-1000) containing oxygen, nitrogen, sulfur and other elements in crude oil, which are dispersed in semi-solid state and dissolved in crude oil. The gum is easily soluble in petroleum ether, lubricating oil, gasoline, chloroform and other organic solvents.
The content of asphaltene in crude oil is less than 1%. Asphaltene is a kind of black solid substance with high molecular weight (more than 1000) and polycyclic structure. It is insoluble in alcohol and petroleum ether, but soluble in benzene, chloroform and carbon disulfide. When the content of asphaltene increases, the quality of crude oil becomes worse.
Hydrocarbons in crude oil are mainly divided into alkanes, cycloalkanes and aromatic hydrocarbons. According to the difference of hydrocarbon composition, it can be divided into paraffin based oil, naphthenic oil and intermediate base oil. Paraffin based oil contains more alkanes; naphthenic oil contains more naphthenic and aromatic hydrocarbons; intermediate cornerstone oil is between the two. Most of the crude oil extracted in China is low sulfur paraffin base. Daqing and other places belong to this kind of crude oil. Among them, the most representative Daqing crude oil has low sulfur content, high wax content and high pour point, which can produce high-quality kerosene, diesel oil, solvent oil, lubricating oil and commercial paraffin. Shengli crude oil has high gum content (29%), high specific gravity (about 0.91) and high wax content (about 15-21%), which belongs to sulfur-containing intermediate base. The gasoline fraction has good lead sensitivity and is rich in naphthenic and aromatic hydrocarbons, so it is a good raw material for reforming.

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