Sour crude refers to a type of crude oil that contains a high concentration of sulfur compounds, specifically hydrogen sulfide (H2S) and carbon dioxide (CO2). It is characterized by its unpleasant odor and sour taste, hence the name "sour" crude. The sulfur compounds in sour crude are corrosive and pose environmental and health hazards.
Typically, the sulfur content in sour crude is higher than 0.5% by weight, whereas sweet crude, its opposite counterpart, contains sulfur content below this threshold. The sulfur content in sour crude can vary significantly, with some sources containing sulfur levels as high as 3-4%. The presence of these sulfur compounds makes sour crude more difficult and costly to refine compared to sweet crude.
Due to the corrosiveness and environmental concerns associated with sulfur content, sour crude requires specialized refining processes to remove the sulfur compounds before it can be used effectively as a fuel or feedstock for petrochemicals. Common methods to reduce sulfur levels include hydrotreating and hydrodesulfurization, which involve the addition of hydrogen gas under high temperature and pressure to convert the sulfur compounds into hydrogen sulfide and other byproducts.
Although sour crude is generally considered less desirable than sweet crude, it still holds significant value as a source of energy and raw material for the petrochemical industry. The quality and characteristics of sour crude can vary depending on the specific region and reservoir it originates from.
The term "sour crude" is derived from two separate terms: "sour" and "crude".
The word "sour" refers to crude oil that contains high levels of sulfur compounds, primarily hydrogen sulfide (H2S) and mercaptans. When crude oil is burned, these sulfur compounds produce a pungent odor similar to that of rotten eggs, hence the term "sour".
The word "crude" in "sour crude" refers to the raw, unrefined form of petroleum that is extracted from the ground. Crude oil is a mixture of hydrocarbons, impurities, and other compounds found naturally in the earth's crust.
Therefore, the term "sour crude" is used to describe crude oil that has a high sulfur content, which imparts a sour smell.