Types of Crude Oil

Monday, September 21, 2009 by ShoXee

Type of crude Oil.

Sweet crude oil is a type of petroleum. The adjective sweet refers to small amounts of hydrogen sulfide and carbon dioxide; sweet crude generally contains less than 0.5% sulfur. This high quality, low sulfur crude oil is commonly used for processing into gasoline and is in high demand, particularly in the United States and China.

Producers of sweet crude oil include:

Saudi Arabia
United Kingdom (Brent Crude)
United States (West Texas Intermediate)

Brent Crude is one of the major classifications of oil consisting of Brent Crude, Brent Sweet Light Crude, Oseberg and Forties. Brent Crude is sourced from the North Sea.
The name 'Brent' comes from the formation layers - Broom, Rannoch, Etieve, Ness and TarbatOil production from Europe, Africa and the Middle East flowing West tends to be priced relative to this oil, i.e. it forms a benchmark. Brent blend is a light crude oil, though not as light as West Texas Intermediate (WTI). It contains approximately 0.37% of sulfur, classifying it as sweet crude, yet again not as sweet as WTI. Brent is ideal for production of gasoline and middle distillates. It is typically refined in Northwest Europe, but when the market prices are favorable for export, it can be refined also in East or Gulf Coast of the United States or the Mediterranean region.

Typical price difference per barrel is about $1 less than WTI, and $1 more than OPEC Basket.
Brent Crude has an API gravity of around 38.6.

Sour crude oil contains the impurities hydrogen sulfide (H2S) and carbon dioxide, or mercaptans. All crude oil contains some impurities. When the total sulfide level in the oil is > 1 % the oil is called "sour". The impurities will need to be removed before this lower quality crude can be refined into gasoline, thereby increasing the cost of processing. This results in a higher-priced gasoline than one made from sweet crude oil. Thus sour crude is usually processed into heavy oil such as diesel rather than gasoline to reduce processing cost. Sour oil is toxic and corrosive, with high levels of hydrogen sulfide. The oil has the smell of rotten eggs, and at high concentrations the inhalation of hydrogen sulfide is fatal. Venezuela is a major producer of sour crude oil.

API degree

A hydrometer scale used to measure the density of petroleum, established by the American Petroleum Institute. Symbol, °API.
When the U.S. Bureau of Standards standardized the Baumé hydrometer scale, it was “discovered that most of the hydrometers in use in the American petroleum industry had been erroneously manufactured to a modulus of 141.5 rather than 140. By 1921 this condition had become so firmly entrenched that the only seeming remedy was to recognize the scale in predominate use and rename it.”

where “G” stands for the specific gravity of the liquid at 60°F in relation to water at 60°F.


API gravity is a specific gravity scale developed by the American Petroleum Institute (API) for measuring the relative density of various petroleum liquids. API gravity is graduated in degrees on a hydrometer instrument and was designed so that most values would fall between 10 and 70 API gravity degrees.

History of development:-

The U.S. National Bureau of Standards in 1916 established the Baumé scale (see degrees Baumé) as the standard for measuring specific gravity of liquids less dense than water. Investigation by the U.S. National Academy of Sciences found major errors in salinity and temperature controls that had caused serious variations in published values. Hydrometers in the U.S. had been manufactured and distributed widely with a modulus of 141.5 instead of the Baumé scale modulus of 140. The scale was so firmly established that by 1921 the remedy implemented by the American Petroleum Institute was to create the API Gravity scale recognizing the scale that was actually being used.

API gravity formulas:-

The formula used to obtain the API gravity of petroleum liquids is thus:
API gravity = (141.5/SG at 60 °F) - 131.5
Conversely, the specific gravity of petroleum liquids can be derived from the API gravity value as SG at 60 °F = 141.5/(API gravity + 131.5) 60°F (or 15 5/9 °C) is used as the normal value for measurements and further tables give adjustments for temperature.

(See ASTM D1298)
Thus, a heavy oil with a specific gravity of 1.0 (i.e., with the same density as pure water at 60°F) would have an API gravity of: (141.5/1.0) - 131.5 = 10.0 degrees API.

Classifications or grades:-

Generally speaking higher API gravity degree oil values have a greater commercial value and lower degree values have lower commercial value. This general rule only holds up to 45 degrees API gravity as beyond this value the molecular chains become shorter and less valuable to a refinery.

Crude oil is classified as light, medium or heavy, according to its measured API gravity.
Light crude oil is defined as having an API gravity higher than 31.1 °API

Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API

Heavy oil is defined as having an API gravity below 22.3 °API.

Oil which will not flow at normal temperatures or without dilution is named bitumen and the API gravity is generally less than 10 °API. Bitumen derived from the oil sands deposits in the Alberta, Canada area has an API gravity of around 8 °API. It is 'upgraded' to an API gravity of 31 °API to 33 °API and the upgraded oil is known as synthetic oil.

American Petroleum Institute-API

The American Petroleum Institute, commonly referred to as API, is the main U.S. trade association for the oil and natural gas industry, representing about 400 corporate members involved in all aspects of the industry. API is involved in lobbying and government liaison on behalf of the American oil and natural gas industries. It takes positions on access, exploration, taxes, trade regulation, environmental regulation, fuels, industry security and climate change.
API's current policy is that emissions from the production and use of oil and natural gas may be contributing to global warming by enhancing the atmosphere's natural greenhouse effect. API coordinates voluntary industry efforts to reduce emissions through technology and improved operational efficiency. API also believes the contribution of possible man-made warming is uncertain as are the extent and timing of potential future impacts. Previously, the API was active in organizing opposition to laws and regulations that would limit smokestack and tailpipe pollution and reduce carbon dioxide emissions. The API was also active in public relations efforts that claim that the greenhouse effect and global warming in general will be beneficial to society, and that the scientific consensus on the dangers of global warming are incorrect.
API University is API’s comprehensive continuing education program for oil and natural gas professionals, in part on-line, such as the interactive computer-based training course "Basic Principles of Petroleum".

API also distributes more than 200,000 copies of its publications each year. The publications, technical standards, and electronic and online products are designed to help users improve the efficiency and cost-effectiveness of their operations, comply with legislative and regulatory requirements, and safeguard health, ensure safety, and protect the environment. Each publication is overseen by a committee of leading industry professionals. API's publications are developed by member company engineers and other professionals.

For example, API 610 is the specification for centrifugal pumps, API 682 governs mechanical seals, and API 677 is the standard for gear units. API also defines the industry standard for the energy conservation of motor oil. SM is the latest specification to which motor oils should adhere since 2004.

API provides vessel codes and standards for the design and fabrication of pressure vessels that help safeguard the lives of people and environments all over the world. YRC.

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