American Petroleum Institute

API gravity

Indication of density of crude oil. The higher the density, the lower is the API gravity.

Atmospheric Distillation

Process which splits crude oil into its constituent fractions.

Barrel or bbl

A standard measure for the volume of crude oil.


The residual product of crude oil vacuum distillation. A black or dark brown solid or semi-solid organic compound that gradually softens and turns to liquid when heated.


Low sulphur crude oil produced in the North Sea and used as the reference against which other crude oils are priced.

Bunker Fuel Oil

Heavy, residual fuel oil used in ships.

Catalytic Reforming

Process which increases the octane of a heavy naphtha stream.


The conversion of large hydrocarbon molecules into smaller ones. Cracking is carried out either at high temperatures (thermal cracking), or with the aid of a catalyst and high pressure (catalytic cracking and hydrocracking). The cracking process enables greater quantities of saturated hydrocarbons suitable for gasoline and other light fractions to be recovered from crude oil.


Residue upgrading process which produces petroleum coke as its heaviest product.

Complex Refinery

Fuels refinery with a vacuum gas oil upgrading process (e.g. FCC).

Crude Oil

Complex mixture of hydrocarbons which constitutes the principal feedstock to a petroleum refinery.

Deep Conversion

Conversion of vacuum residue to lighter and more valuable products.

Deep Conversion Refinery

Refinery which has in its configuration the facility to upgrade vacuum residue to lighter products.


Product recovered during atmospheric or vacuum distillation process.

Dubai Crude

High sulphur crude oil produced in the Middle East and used as a reference against which other crude oils are priced.


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Engineering, Procurement and Construction.

Fluidized Catalytic Cracking (FCC)

Process which upgrades vacuum gas oil to lighter more valuable refined products, primarily gasoline.

Flue Gas Desulphurisation (FGD)

Process for removing the sulphur from the combustion gases produced by the burning of high sulphur fuels

FOB(Free on Board)

A pre-delivery pricing basis. This generally refers to the price at a refinery or terminal at the point of loading

Fuel Gas

Light refinery gases used as refinery fuel.

Fuel Oil

Heaviest and least valuable product from the refining of crude oil. It is typically used as an industrial fuel or as a fuel on ships.


Refined product primarily used as a fuel for cars. Sometimes referred to as Petrol (in the UK) or Mogas (in the US)

Gas Oil

Term used to describe both automotive diesel oil and heating oil which are both made from similar hydrocarbon material.

Gross Refining Margin(GRM)

Gross Refining Margin. Product revenues less feedstock costs (hence not deducting other variable fixed or financial costs).

Heavy crude

Crude oil with a high specific gravity and a low API gravity due to the presence of a high proportion of heavy hydrocarbon fractions and metallic content.


Fuel oil containing greater than three percent sulphur (High Sulphur Fuel Oil)


Materials which are composed of hydrogen and carbon.

Hydro Desulphurisation

Process which uses hydrogen to remove sulphur from refined products.

Hydro skimming Refinery

Represents the simplest common refinery configuration comprising atmospheric distillation, hydrotreating and naphtha reforming.


Same as Hydro Desulphurisation


‘Inside Battery Limits’ refers to main processes for a given project.


Process which increases octane number of light naphtha.


General term for jet and lamp kerosene.

Light Crude

Crude oil with a low specific gravity and high API gravity due to the presence of a high proportion of light hydrocarbon fractions and low metallic compound.

Light Ends

The more volatile products of petroleum refining; eg. butane, propane, gasoline

Liquefied Petroleum Gas

A mixture of propane and butane produced on the refinery.


Process to remove mercaptan sulphur from Kerosene and LPG.

Middle Distillate

General term for kerosene and gas oils.


Refined product used as a constituent in gasoline, a feed to a naphtha isomerisation unit or a petrochemical feedstock.

Naphtha Isomerisation

Process which increases the octane of light naphtha. (and ethane)


Price of product at the originating location derived from final selling price at the destination market reduced by an amount to be incurred to make the product reach the destination market (including freight, losses, handling costs, duties etc).


Measure of the combustion performance of a fuel in a gasoline engine.


Out Side Battery Limit, refers to associated utilities etc.

Petroleum Coke

Solid ‘coal like’ material used as a fuel or for the production of anodes for the aluminum smelting industry.

Reduced Crude Oil

Crude oil that has undergone at least one distillation process to separate some of the lighter hydrocarbons. Reducing crude lowers its API gravity, but increases the handling safety by raising the flash point.


A plan used to separate the various components present in crude oil and convert them into usable products or feedstock for other processes.

Refined Products

Products from the refining of crude oil in a petroleum refinery.

Reformulated Gasoline

Specially formulated gasoline required in certain regions of the United States aimed at reducing range of undesirable emissions (notably ozone precursors).


Fuel Oil

Heavy fuel oils produced from the non-volatile residue from the fractional distillation process. Heavy oils that are "leftovers" from various refining processes. Heavy black oils used in marine boilers and in heating plants.


Heaviest stream from the distillation process.


An element that is present in crude oil and natural gas as an impurity in the form of its various compounds.

Sour Crude Oil

High sulphur crude oil.

Sweet Crude Oil

Low sulphur crude oil


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Vacuum Distillation

Distillation of long residue under vacuum to recover vacuum gas oil.

Vacuum Gas Oil (VGO)

Distillate product recovered from the vacuum distillation of long residue.

Vacuum Residue

Heavy residue (fuel oil) stream remaining after the recovery of vacuum gas oil from long residue


Process which reduces the viscosity of vacuum residue.

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