A crude oil assay is the chemical evaluation of
crude oil feedstocks by
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
testing laboratories. Each crude oil type has unique
molecular and
chemical
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...
characteristics. No two crude oil types are identical and there are crucial differences in crude oil quality. The results of crude oil assay testing provide extensive detailed
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
analysis data for refiners, oil traders and producers. Assay data help refineries determine if a crude oil feedstock is compatible for a particular petroleum refinery or if the crude oil could cause yield, quality, production, environmental and other problems.
The assay can be an inspection assay or comprehensive assay. Testing can include crude oil characterization of whole crude oils and the various boiling range
fractions
A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...
produced from physical or simulated distillation by various procedures. Information obtained from the petroleum assay is used for detailed refinery engineering and client marketing purposes. Feedstock assay data are an important tool in the refining process.
See also
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API gravity
The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks ...
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Cetane index
Cetane index is used as a substitute for the cetane number of diesel fuel. The cetane index is calculated based on the fuel's density and distillation range (ASTM D86). There are two methods used, ASTM D976 and D4737. The older D976, or "two-va ...
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K factor (crude oil refining) The K factor or characterization factor is defined from Rankine boiling temperature °R=1.8Tb and relative to water density ρ at 60°F:
K(UOP) = \sqrt / \rho
The K factor is a systematic way of classifying a crude oil according to its paraffi ...
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Octane rating
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Petroleum coke
Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracki ...
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PONA number The PONA number is an index for oil components. It is used to determine the paraffins (P), olefins (O), naphthenes (N) and aromatics (A) content of FCC ( fluid catalytic cracking) and coker ( visbreaker) gasoline.
The PONA number is significant i ...
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Ramsbottom carbon residue
Ramsbottom carbon residue (RCR) is well known in the petroleum industry as a method to calculate the carbon residue of a fuel. The carbon residue value is considered by some to give an approximate indication of the combustibility and deposit formi ...
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Reid vapor pressure Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products. It is defined as the
absolute vapor pressure exerted by the vapor of the liquid and any dissolved gases/moisture at 37.8 °C (100 ...
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Saturate, aromatic, resin and asphaltene
Saturate, Aromatic, Resin and Asphaltene (SARA) is an analysis method that divides crude oil components according to their polarizability and polarity. The saturate fraction consists of nonpolar material including linear, branched, and cyclic sat ...
(aka SARA)
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True vapor pressure
References
External links
Energy Institute Crude Oil DataUS Dept. of Energy Assay Manual PDF
Oil refining
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