Abandoned well

A well (oil, natural gas, or water injection) not in use because it was a dry hole originally, or because it has ceased to produce economical quantities of oil and/or natural gas, or has become unusable. Regulations require the plugging of abandoned wells to prevent the seepage of oil, gas, or water from one stratum of underlying rock to another.

Able-bodied seaman (AB)

A member of an LNG crew, with three years of sea service, certified by examination to perform all the duties of an experienced seaman. A typical LNG ship carries five ABs in her crew complement. 

Acid gas

A gas that contains compounds, such as CO2, H2S or mercaptans, that can form an acid in solution with water.

Acquiring shipper

In the context of capacity release, a shipper who acquires firm capacity rights from a releasing shipper. Also known as replacement shipper. 


A term describing a thermodynamic process in which no heat is added to or removed from the system.


The confirmed or official dimensions of an LNG ship.

Agency service

An arrangement that allows a gas buyer to give an agent authority to act on the buyer’s behalf to arrange or administer pipeline transportation and/or sales services. 

Aggregate receipt points

1) a hub where different supply sources intersect on a gas pipeline; 2) multiple producer meters entering a pipeline. 


1) an entity acting on behalf of groups of producers to collect producer supplies and sell the gas in to end-users. Prior to deregulation in the US, a limited number of aggregators operated. Aggregators do not take title to the gas but simply find markets and negotiate prices for pools of producers. Also called core transport agent; 2) an entity that bargains on behalf of a large group of consumers to achieve the lowest possible price for utilities such as electricity and gas. The firm aggregates (combines) many smaller customers into one large customer for purposes of negotiation and then purchases the utility commodity on behalf of the group.

Alternative fuel capability

The on-site availability of a power plant to burn more than one fuel.

Ambient temperature

Environmental temperature unaffected by other heat sources, such as radiation from artificial objects.

American National Standards Institute (ANSI)

The co-ordinating organization for US federated national standards system.

Annual contract quantity

The annual delivery quantity contracted for during each contract year as specified in a gas sales or LNG contract. It may be expressed either as a standalone number or as a multiple of the Daily contract quantity.

Annual delivery programme (ADP)

A document agreed by buyers and sellers setting out the quantities and timing of LNG cargoes for the coming contract year. For an ex-ship sale, the ADP deals with the dates on which ships will deliver LNG to terminals. For a Free on board (FOB) sale, the ADP covers the dates of arrival of the buyers’ ships at an LNG plant. The ADP provides a basis for decisions on how buyers and sellers will operate their facilities during the year. Usually, procedures adopted to develop the ADP are agreed on in the Sales and purchase agreement (SPA). 


The purchase and sale of an asset in order to profit from a difference in its price, usually on different exchanges or marketplaces. Where appropriate infrastructure exists, LNG offers the opportunity for price arbitrage between different gas markets.

Articles of agreement

The document containing all particulars relating to the terms of agreement between the Master of the LNG vessel and the crew. Sometimes called ship’s articles or shipping articles.


The price asked by those recently willing to sell a commodity at a point in time. The asking price is considered by commodity purchasers in a market-making or price-discovery context.

Associated gas

Natural gas found and produced in association with oil. It may be held in solution with the oil, or be contained within the oil reservoir as a separate cap of gas. In these fields, natural gas production levels fluctuate with oil production.


Behind or towards the rear of a ship. If a vessel moves backwards it is said to move astern, opposite to ahead.

Atlantic basin market

See LNG markets

Average daily quantity (ADQ)

The monthly contracted quantity of gas divided by the number of customers’ operating days in that month.

Average demand

Measure of the total of energy loads placed by customers on a system divided by the time period over which the demands are incurred.