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Petroleum Glossary


The American Petroleum Institute (API) is a United States trade association that represents 400 corporations in the petroleum industry.

Abel tester

A closed-cup flash tester. Used to test the flash point of kerosene and other distillates.


The pH of an oil, which may or may not influence the behavior of the oil, depending on the exact mechanism of by which the pH is achieved.

Air-Fuel Ratio

The ratio of air consumed to fuel consumed, by weight, in an internal combustion engine or other fuel-burning apparatus. Has impact on performance and efficiency.


Any hydrocarbon in chains. Includes the alkanes, alkenes, and alkynes among many others.


The largest class of hydrocarbons. These include linear and branched chain molecules typically used in the production of fuel.

Annular Blowout Preventer

Invented in 1952, these are often referred to as “Hydrils.” These blowout preventers use a rubber seals to close around the drill string and seal the well.

API Gravity

The standard by which all crude oils are measured. API gravity is used to determine the specific gravity of crude oil and thus its density. Lighter crudes are more valuable because they are more easily refined into gasoline. Crude with an API gravity of 10 is equivalent in density to water.

Aromatic Hydrocarbon

Any hydrocarbon that contains a dream structure in which all of the bonds are of intermediate character between single and double bonds. They are often referred to as 1.5 bonds.


Inorganic residue that remains from burning combustible material. It is the same as ash that remains after wood is burned.


Insoluble, semi-solid particles. They have a high carbon to hydrogen ratio and are used in the production of asphalt.


American Society for Testing Materials. This is the group that develops products for testing grade of petroleum products.

Atomization characteristics

How well particular oil can be broken into fine particles via mechanical means.


A volume measure equal to 42 U.S. gallons or approximately 160 liters.


Abbreviation for barrel.

Benchmark Crude

Benchmark crude oils are used as references for pricing oils. There are approximately 161 different benchmark oils, of which the main three are West Texas Intermediate, Brent Crude, and Dubai Crude.


An aromatic hydrocarbon which is obtained chiefly from coal tar. It is used as a solvent for resins and in dye manufacture. It is one of the top 10 chemicals produced by volume.


Brake horsepower or British Horsepower. This is a standard measure of power output for engines.


Any diesel fuel that is created through the transesterification of fat. Comes in various mixtures of 100%, 20%, 5%, and 2%.


Any fuel that is derived from biological carbon fixation that has occurred relatively recently.


Methane produced from fermentation. Often produced by farmers via fermentation of animal waste and used to offset fuel costs.


Bitumen is the geological term that refers to the sticky, highly viscous semi-solid hydrocarbon present in most natural petroleum. It is alternatively called pitch, resin, and asphaltum.

Blowout Preventer

A mechanical device designed to prevent oil from escaping a well during the process of drilling. Called BOP for short. Blowout preventers come in two varieties: ram style and annular. In general, both styles are combined for added security. A single BOP usually contains at least two annular BOPS and three or more Ram BOPS

Bonny Light

This crude oil comes from Nigeria and has an API gravity of 32.9°. Its sulfur content is 0.16%.

Brent Crude

Named after a goose, this light, sweet crude comes from the north sea. It has an API gravity of 38.06 and a sulfur content of 0.37%.

British Petroleum

The former name of petroleum company currently called BP. It is the third largest publicly traded oil company in the world with oil reserves up 18 billion barrels and the annual revenues of $308,000,000,000. It is headquartered in London, England.

BS & W

Bottom sediment and water is a reference to how much water and sediment contamination is in a reserve.

BS & W Monitor

An instrument that detects water in petroleum. The monitor works through changes in the capacitive reactance caused by changes to the dielectric constant of the oil that are induced by water.


British Thermal Unit. The amount of heat required to raise the temperature of 1 lb of water by 1 degree Fahrenheit.


An alcohol based fuel that is considered to be closer to gasoline than most others. Can be used in engines without any alterations.

C/H Ratio

Carbon to Hydrogen ratio


The amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius.


The element with atomic number six. Carbon is the basis of all life and is one of the primary components of hydrocarbons used for fuel.


A compound that increases the speed with which a chemical reaction occurs, but which does not enter into the reaction. A catalyst can be recovered after a reaction is over and reused.


Alternative to the term Centigrade below that references physicist Anders Celsius who developed the temperature scale, which sets the freezing point of water at 0 and the boiling point at 100.


Temperature scale in which 0 is the point for water freezing and 100 the point at which water boils. Abbreviated with a capital C.

Chevron Corporation

The fifth largest publicly traded oil company in the world. It has oil reserves of 10.5 billion barrels and revenue of $204,000,000,000. It is headquartered in California.

Cloud Point

Temperature at which wax begins to and form a solid in a fuel.

Cold Heavy Oil Production with Sand (CHOPS)

In this process sand filters are removed from pumping equipment and sand is produced along with oil. The two are then separated above ground. In general, CHOPS is capable of recovering a 5 to 6% of oil in a given a well.


The sixth largest publicly traded oil company in the world with oil reserves of 8.3 billion barrels and revenue of $198,000,000,000. It is headquartered in Huston Texas.


The oxidation or destruction of a component. This is particularly troublesome in oil pipelines and tankers in which the metal is damaged by contaminants within the oil.


The process in refining oil in which larger hydrocarbons are broken down into smaller components.

Cutter stock

Light petroleum used to reduce viscosity of heavier oil. These are used to “cut” heavy oil in order to make it easier to transport.

Cyclic Steam Stimulation (CSS)

Steam is injected into a vertical well for several weeks or even months in order to liquefy the petroleum. Oil is then pumped for as long as possible before the procedure is repeated again. It is sometimes referred to as “huff and puff.”


Mass of a unit of volume. It is often expressed as mg/L.


In an engine, this is the combustion of the fuel after spark occurs. It produces a characteristic metallic sound, or knock.

Diesel index

Obtained by multiplying the API gravity by the aniline point (the temperature at which a chemical called aniline and diesel mix) of a Diesel fuel, divided by 100. It indicates the quality of the fuel.


The process of heating a liquid to the boiling point, then allowing it to condense in order to collect molecules of different sizes.

Doctor test

A qualitative method of determining whether oil is "sour" or "sweet".

Double Hull

An oil tanker with two hulls. These are generally considered to be safer in the event that the tanker runs aground.

Dubai Crude

This is a light and sour crude with and API gravity of 31°. Its sulfur content is 2%.


Automobile fuel in which 85% is ethanol.


A liquid mixture of two or more liquid substances that do not dissolve in one another. One liquid is held in suspension, as in many salad dressings


The most common alcohol based fuel. It comes in various dilutions of 100%, 85%, 70%, and 15%.


The removal of oil from a well. The total amount of oil that can be recovered from most wells is in the range of 60%.

Extra-heavy Crude

Crude oil with an API gravity of less than 10. The oil sinks in water.


The largest of the “Supermajors” publicly traded oil companies. It has reserves of 72 billion barrels of oil and revenue of over $383,000,000,000. It is headquartered in Huston, Texas.


Temperature scale in which 32 is set as the freezing point of water and 212 as the boiling point. Generally only used in the United States. Conversion to Fahrenheit from Celsius: F = 9/5C + 32, where C is the temperature in Celsius.

Flash Point

The lowest temperature at which a liquid will generate sufficient vapor to ignite.

Fossil fuel

Fuels formed by natural processes such as anaerobic decomposition of dead and buried organisms. Also fuels include coal, petroleum, and natural gas.


A separate identifiable part of crude oil. Gasoline and kerosene are two different fractions of crude.

Fuel oil

The heavy distillates of the oil refining process. Generally used for power stations and in large ship boilers. Contains a high degree of contaminant and produce a great deal of pollution.


Refers to petroleum products which can be transport in a pipeline in succession, one after the other, without need for space between them.

Global warming

The continuing rise in the average temperature of Earth’s atmosphere and oceans.

Green Diesel

Diesel fuel derived for renewable resources, but which is produced for a standard fractionation rather than transesterification.

Greenhouse effect

The process by which thermal radiation from a planetary surface is absorbed by at the spirit gases and we radiated in all directions.

Greenhouse gas

The gas in the atmosphere that absorbs any bits radiation with them a thermal in for reader range. The primary greenhouse gases in the Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

Heavy Crude

Heavy crude oil has an API gravity of less than 20. The largest deposits of heavy crude are found in Canada and Venezuela.


Higher heating value


A mechanical device which is used to create a emulsion by rapidly mixing the two immiscible substance together.



Hubbert Curve

A model of oil production over time. The rate of production of individual wells grows exponentially from discovery until a peak is reached, at which point production steadily, and sometimes swiftly, declines.

Hydraulic Fracturing (Fracking)

The process used to recover oil that is trapped in sedimentary rocks. Generally consists of drilling followed by the injection of air or water, which may or may not have chemicals mixed in.


An organic compound composed of hydrogen and carbon that makes up the majority of petroleum and which is refined to make fuels.


Hydrogen is the smallest of all atoms. Two hydrogen atoms combined together constitute molecular hydrogen, which can be burned as fuel or used in fuel cells.


An instrument for determining the gravity (density) of a liquid.

International Oil Company (IOC)

Any oil company that is publicly traded.


The process of adding or removing electrons from atoms, thereby creating charged particles called ions. Extremely high temperatures, electrical discharge, and nuclear radiation can cause ionization.


British Institute of Petroleum.

Iraqi National Oil Company (INOC)

The National Oil Company of Iraq. It was founded in 1966 and is capable of production capacity of three million barrels of oil per day.

Isthmus-34 Light

This is a sour crude with and API gravity of 33.74° and a sulfur content of 1.45%. It is produced in Mexico.


The organic matter found in sedimentary rock that contains a mixture of organic chemicals and hydrocarbons and so would form. The solid hydrocarbon part is referred to as bitumen.

Kuwait Petroleum Corporation

The state oil company of Kuwait. It is proven reserves of 111 billion barrels of oil and estimated revenue of $67,000,000,000.

Latent Heat

The heat required to change the state of a substance from solid to liquid or from liquid to gas.


This occurs in tanks when a high density fuel is mixed with a low density fuel and the lower density floats atop the higher density. The same phenomenon is observed in salad dressing that are allowed to sit for a long time.


Lower Heating Value


A term used to refer to tankers and barges taking on oil or oil derivatives.

Light Crude

Light crude is any crude with and API gravity of greater than 31. It is valued for the ease with which it can be converted to gasoline.

Light Ends

The more volatile products of petroleum refining; eg. butane, propane, gasoline. These are the smallest hydrocarbons and often the most valuable


A measure of capacity in the metric system equal to  0.908 US quarts dry and 1.0567 US quarts wet.

Long Ton

Measure of weight equal to 2,240 pounds.


The simplest of all hydrocarbons. It consists of a single carbon with four attached hydrogen and is a gas at room temperature.

Metric Ton

Measurement equal to 1000 kg or 2204 pounds


One thousandth of a millimeter or one millionth of a meter. Approximately 0.00004 inches.

Middle Distillate

Heating oil, diesel fuels, and kerosene fill this category, which constitutes the elements of crude with medium density.


Also called Sumatran light, this is a light and sweet crude with and API gravity of 35° and a sulfur content of only 0.08%.


Millimeter. 1/1000 of a meter.


The smallest division of a compound that still retains or exhibits all the properties of the compound. A molecule of water  for instance.


Volatile, colorless product of petroleum distillation. Used primarily as paint solvent and cleaning fluid.


One of three basic hydrocarbon classifications found naturally in crude oil. They are typically used in the production of petrochemicals.

National Iranian Oil Company (NIOC)

The National Oil Company of Iran with oil reserves of 138 billion barrels and revenues of $78,000,000,000. It has a production capacity of four million barrels of crude per day.

National Oil Company (NOC)

Any oil company controlled by a state and which is not publicly traded.

National Oil Corporation (NOC)

The state oil company of Libya. It controls reserves of 50 billion barrels of oil. Annual revenue is estimated at roughly $45,000,000,000.

Neutralization number

The weight in milligrams of base (alkali) needed to neutralize the acidic material in one gram of oil. The higher the neutralization number, the more acidic the oil is.

Nigerian National Petroleum Corporation (NNPC)

The state oil company of Nigeria. It controls oil deposits of 64 billion barrels and earned roughly $12,000,000,000 in profit and in 2006. It has production capacity of 2.39 million barrels of oil per day.


Crude petroleum and other hydrocarbons in liquid form

Oil Shale

Oil shale refers to a type of crude oil that is trapped in sedimentary rock.

Oil Tanker

Ships used for transporting petroleum across water. Oil tankers can be double-hulled or single-hulled. Oil tankers, the variety of sizes ranging from a those that can safely carry tens of thousands of barrels of oil to those that can carry over two million barrels of oil.


A class of unsaturated paraffin hydrocarbons. These include things like ethylene and propylene.


The Organization of Petroleum Exporting Countries is an intergovernmental organization of 12 nations that export oil. The countries that make up OPEC are: Algeria, Angola, Ecuador, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela. OPEC is headquartered in Vienna.

OPEC Reference Basket (ORB)

This is not a specific crude, but rather is a weighted average of petroleum that comes from OPEC countries. There are 11 different oils combined into the orb be. It has an average API gravity of 32.7° and an average sulfur content of 1.77%.


Space left in a container to allow for expansion during temperature changes it may undergo during shipment.


Combining elemental compounds with oxygen. This is the process that leads to rust.

Oxidizing agent

Any substance such as oxygen and chlorine , that can accept electrons.


The use of ozone for disinfection or odor control.


Solids that are suspended in a gas or liquid.

Peak Oil

On a global scale, this term refers to the point at which extraction of petroleum is at its maximum and after which production of oil can only diminish. Peak oil can also be applied to individual wells and is the point at which maximum oil extraction for that well occurs.


An intermediate chemical derived from petroleum. It includes such things as ethylene, benzene, toluene, and xylene.

Petroleos de Venezuela (PDVSA)

The state owned petroleum company of Venezuela. It has 77 billion barrels of conventional crude oil and an estimated 235 billion barrels of extra-heavy crude.


Naturally occurring crude oil consisting of a complex mix of hydrocarbons of various molecular weights and other liquid organic compounds as well as inorganic compounds.

Petroleum Reserve

A commercially recoverable deposit of oil. Subdivided into proven, unproven, and strategic reserves. A new category was created into 2007 termed resources.


pH is an expression of how basic or acidic something is. pH range is from 0 to 14, where 0 is most acidic, 14 most basic, and 7 is neutral.


An alcohol derived from benzene.


Pipelines are used to transport a number of substances including natural gas, fuels, hydrogen, water, and petroleum.


The destruction of water or air such that it is unusable due to toxicity or risk of illness.

Polycyclic Aromatic Hydrocarbon (PAH)

Atmospheric pollutants that are byproducts of burning aromatic hydrocarbons. Many of these can be found in cigarette smoke.


A chemical formed by the combining many single monomers.


Process of combining two or more simple molecules to form a single large molecule called a polymer. Most plastics are made this way.

Pour Point

Lowest temperature at which oil will flow freely.

Primary Extraction

The primary stage of recovery after an oil well has been drilled. Oil flows to the surface under natural mechanisms that include pressure from the expansion of natural gas as well as gravity drainage of oil from upper parts of the well and displacement of oil by water. Primary extraction is able to recover 5 to 15% of the total amount of petroleum within a well.

Proven Reserve

A petroleum reserve in which there is a 90% certainty that the petroleum can be recovered.

Quatar Petroleum (QP)

The state oil company of Quatar with total recoverable reserves capacity of 170 billion barrels of oil and production capacity of one million barrels per day. Profits of roughly nine billion dollars.

Ram Style Blowout Preventer

First invented in 1922, these are not intended to completely seal a well but rather are used to reduce the flow of oil to a manageable rate to allow time for capping. Modern ram bops are termed shear rams, and are capable of cutting through drill pipe to completely stop the flow of oil and the well.

Reduced Crude Oil

Crude oil that has undergone at least one distillation to separate some of the lighter hydrocarbons. Reducing crude lowers its API gravity.

Reducing agent

Anything, such as iron or the sulfide ion that will give up electrons. This is the opposite of an oxidizing agent.


The process of separating crude oil into useful components including gasoline, diesel fuel, jet fuel, fuel oil, and other products.


Heavy fuel oils produced from the non-volatile fractional distillation process. Heavy oils that are leftovers after refining.


The term introduced in 2007 that adds categories for contingent and prospective resources in addition to proven and unproven reserves. Contingent reserves are those that are potentially recoverable, but for which commercial development is not yet feasible due to one or more contingencies. Prospective reserves or prospective resources refer to locations where oil may be found, but for which no actual discovery has occurred.

Royal Dutch Shell

The second largest publicly traded oil company in the world. It has oil reserves of over 20 billion barrels and annual revenue of $368,000,000,000. It is headquartered in The Hague, Netherlands as well as London, England.

Saudi Aramco

The largest oil company in the world and perhaps the world’s most valuable privately held company with an estimated total worth of 2.2 27 trillion in U.S. dollars. It has total estimated petroleum reserves of 260 to 303,000,000,000 barrels of oil and production capacity of 8.3 million barrels per day. Revenue has been estimated at $233,000,000,000 per year.

Second Generation Biofuels

Any biofuel produced from sustainable feedstock which is not diverted from either in animal or human food chains.

Secondary Extraction

Secondary recovery of petroleum occurs after natural forces no longer drive oil to the surface. Secondary recovery depends on mechanical methods to increase pressure in the well including the injection of natural gas or the use of pumps. Secondary recovery accounts for 30% of the total output obtained from an oil well.

Short ton

An measure of weight equal to 2,000 lbs.

Single Hull

In reference to oil tankers, this means the ship has only one hull structure as compared to those with two.


Formation of hard deposits on pistons in an engine as the result of contaminants, usually sodium, vanadium and sulfur.


The National Oil Company of Algeria. It has proven reserves of 39 billion barrels of oil and produces approximately 620,000 barrels per day. It had net income in 2010 of $2.4 billion.

Sour Crude

Sour crude has a sulfur content of greater than 0.5% by weight.

Specific gravity

Weight of a particle, substance or chemical solution in relation to an equal volume of water at 15C.

Specific heat

The quantity of heat required to raise the temperature of a unit weight of a substance by 1 degree.


To make something resistant to change. Organic material can be stabilized by bacteria and will not give off obnoxious odors.

Steam Assisted Gravity Drainage (SAGD)

Two horizontal wells are drilled, with one well approximately 5 m above the other. Steam is injected into the upper well, sometimes along with other chemicals, and heats the crude oil to increase liquidity. Oil is then collected as it drains into below were well. SAGD can reach efficiencies of up to 60%.


Standard Temperature (25C) and Pressure (300 mm Hg).


All products that can be gained by the first round of refining before cracking and other secondary processes are implemented.

Strategic Reserve

Government-controlled oil stockpiles maintained to protect a country’s economic and National Security.


Occurs in blended fuels where the denser fuels settle to the bottom and lighter fuels rise to the top.


An element that is present in crude oil and natural gas as an impurity. Responsible for acid rain.

Super Tanker

Any oil tanker capable of transporting more than 320,000 metric tons.


Surface-active agent. These products are basically soaps and help substances that are immiscible, like water and oil, to mix.

Sweet Crude

Sweet crude has a sulfur content of less than 0.5% by weight.


This is often referred to as “the world’s costliest oil.” It comes from a single field in Malaysia and has an API gravity of 45.2° and a sulfur content of 0.0343%, making it an exceptionally light and sweet.

Tertiary Extraction

The final stage of oil extraction. Methods are applied it to increase the liquidity of the oil and often include the injection of heat and chemicals. Increasingly, oil-eating bacteria are being used in this step. Accounts for 5 to 15% of the total amount that can be recovered from a well.

Toe-to-Heel Air Injection (THAI)

The newest method in heavy oil extraction. Air is injected into the tunnel or for end of the well and then a fire is ignited in order to burn heavier components of the oil. The lighter elements are then extracted. The fire is self-limiting that due to the lack of oxygen in the well.

Topped Crude Oil:

Oil from which the light hydrocarbons have been removed.

Total Existent

All of the inorganic components and hydrocarbon existing in a fuel.

Total SA

The fourth largest publicly traded oil company in the world with oil reserves of 10.5 billion barrels and revenue of $229,000,000,000. It is headquartered in Paris, France.


Poisonous to a living organism.


The degree of how poisonous a substance is.

Unproven Reserve

Geologically equivalent to proven reserves, their unproven status rests on technical, regulatory, or political issues. Unproven reserves fall into two categories: probable and possible. A probable reserve has a 50% chance for petroleum recovery and is termed in the industry P50. A possible reserve, also called a P10 reserve, has a 10% chance of recovery.

Vapor Extraction (VAPEX)

In this method of oil extraction, two horizontal Wells are drilled, with one well approximately 5 m above the other. Chemical solvents or injected into the upper well in order to liquefy the petroleum, which drains to the lower well and is extracted.

West Texas Intermediate

The most famous of the benchmark crude oils. WTI is a light, sweet crude with and API gravity of 39.6° and a sulfur content of 0.24%.