Associated Gas — Associated Gas is found in reservoir where gas is dissolved in crude oil (solution gas) and in some cases also in contact with underlying gas-saturated crude (gas-cap gas). Both are call associated gas.

Blue Water Gas — also called "water gas" Made in a cyclic process in which an incandescent bed of coke or coal is alternately subjected to blasts of air and steam. The gas consists mainly of equal proportions of carbon monoxide and hydrogen and has a gross heat content of about 300 Btu/ft3 (see also carbureted water gas).

Carbureted Water Gas — (carbureted blue gas) the gas resulting from the enrichment of blue water gas during its manufacture by a simultaneous process of light distillate, gas oil or fuel oil gasification. The gas has a gross heat content of about 500 to 550 Btu/ft3.

Coal Bed Methane (CBM) — natural gas extracted from coal beds.

Coal Gas or Coke Oven Gas — a manufactured gas made by destructive distillation ("carbonization") of bituminous coal in a gas retort or by-product coke oven. Its chief components are methane (20 to 30%) and hydrogen (about 50%). This gas generally has a gross heating value of 500 to 550 Btu/ft3. When the process takes place in a closed oven (with gas as a by-product of coke production) it is generally designated as "Coke Oven Gas," and when produced in retorts it is called "Coal Gas."

Condensate — a liquid/hydrocarbon mixture of 45 to 65 degrees A.P.I. gravity, which may be recovered at the surface from some non-associated gas reservoirs.

Dry Gas — dry gas is almost pure methane and occurs in the absence of liquid hydrocarbons or by processing natural gas to remove liquid hydrocarbons and impurities.

Greenhouse Gas — Atmospheric gases that are transparent to solar (short-wave) radiation but opaque to long-wave (infrared) radiation, thus preventing long-wave radiant energy from leaving Earth's atmosphere. The net effect of these gases is a trapping of absorbed radiation and a tendency to warm the planet's surface. The greenhouse gases most relevant to the oil and gas industry are carbon dioxide, methane and nitrous oxide.

Hydrocarbons — an organic compound containing only carbon and hydrogen and often occurring in nature as petroleum, natural gas, coal and bitumens or in refined products such as gasoline and jet fuel.

Liquefied Natural Gas (LNG) — natural gas that has been converted to a liquid by cooling to minus 258°F (-161°C) at atmospheric pressure. Liquefying natural gas reduces the fuel’s volume by 600 times, enabling it to be shipped economically from distant producing areas to markets.

Liquefied Petroleum Gas (LPG) — any hydrocarbon mixture, in either the liquid or gaseous state, the chief components of which consist of propane, propylene, butane, iso-butane, butylene or mixtures thereof in any ratio.

Low Pressure Gas Distribution System — a gas distribution system, or the mains of a segment of a distribution system, operated at low pressures of less than 15 inches water column.

LPG Air Mixtures — mixtures of liquefied petroleum gas and air to obtain a desired heating value and capable of being distributed through a distribution system also used for stand-by and peak-shaving purposes by gas utilities.

Manufactured Gas — combustible gases derived from primary energy sources by processes involving chemical reaction. For instance, gas produced from coal, coke or liquid hydrocarbons (see also town gas).

Meter Gas — a mechanical device for automatically measuring quantities of gas.

Natural Gas — naturally occurring hydrocarbon gases found in porous rock formations. Its principal component is usually methane. Non-hydrocarbon gases such as carbon dioxide and hydrogen sulfide can sometimes be present in natural gas.

Natural Gasoline — those liquid hydrocarbon mixtures containing essentially pentanes and heavier hydrocarbons which have been extracted from natural gas.

Natural Gas Liquids (NGL) — a term used for those mixtures of hydrocarbon fractions that can be extracted in liquid form from natural gas. In the widest sense, they can comprise any combination of the following; ethane, propylene, propane, butylene, isobutane, n-butane, pentanes, hexanes, heptanes, and octanes.

Non-associated Gas — Structures from which only gas can be produced economically called non-associated gas (or unassociated gas).

Producer Gas — a gas manufactured by burning coal Qr coke with a regulated deficiency of air, normally saturated with steam. The principal combustible component is carbon monoxide (about 30%) and the gross heat content is between 120 and 160 Btu/ft3.

Refinery Gas — a gas resulting from oil refinery operations consisting mainly of hydrogen, methane, ethylene, propylene and the butylenes. Other gases such as nitrogen and carbon dioxide may also be present. The composition can be highly variable and the heat content can range from 1,000 to 2,000 Btu/ft3.

Sour Gas — sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S).

Sweet Gas — natural gas that contains little or no hydrogen sulfide.

Tight Gas — natural gas produced from relatively impermeable rock. Getting tight gas out usually requires enhanced technology applications like hydraulic fracturing. The term is generally used for reservoirs other than shale.

Town Gas — gas piped to consumers from a gas plant. The gas can comprise both manufactured gas (secondary energy) and natural gas (primary energy) used for enrichment.

Unaccounted for gas — the difference between the total gas available from all sources and the total gas accounted for as sales, net interchange and company use. The difference includes leakage or other actual losses, discrepancies due to meter inaccuracies, variations of temperature, and pressure and other variants.

Wet Gas — produced gas that contains natural gas liquids.