Sale for resale

A sale of natural gas to a customer who will in turn sell that gas to someone else.

Sales and purchase agreement (SPA)

A definitive contract between a seller and buyer for the sale and purchase of a quantity of natural gas or LNG for delivery during a specified period at a specified price. See Annual delivery programme (ADP) and Heads of agreement (HOA).

Sales gas

Natural gas treated and conditioned to meet gas purchaser specifications.

SCADA system (supervisory control and data acquisition)

A computerised automation system that brings together the following technologies: telemetry, telecontrol, supervisory control, and data acquisition, analysis and presentation. When a SCADA system is employed in an LNG process plant or pipeline, information from remote data gathering devices is made available to a central location. Moreover, information gathered can be used by a human operator as the basis for issuing commands to the remote locations.


Process by which nominations are first consolidated by receipt point and by contract, and verified with upstream and downstream parties. If the verified capacity is greater than or equal to the total nominated quantities, all nominated quantities are scheduled. If verified capacity is less than nominated quantities, nominated quantities will be allocated according to scheduling priorities.


Statement on the condition of the vessel for the trade or service in which it is employed.

Seaworthiness certificate

Certificate issued by a classification society surveyor to allow a vessel to proceed after she has met with a mishap that may have affected her seaworthiness. It is frequently issued to enable a vessel to proceed, after temporary repairs have been effected, to another port where permanent repairs are then carried out.

Second mate

Ship’s navigation officer; keeps charts (maps) up to date and monitors navigation equipment on bridge. See Crew

Secondary market

In the gas industry, this is the market for re-selling unneeded pipeline-transportation capacity.

Send-out capacity

The volume of natural gas that can be converted by a liquefaction facility and subsequently shipped over a specified period of time.


A vessel used to separate a multiphase mixture of fluids into its separate phases, for example, vapour, oil, water, solids.

Shale gas

Gas trapped in pores within shale deposits. Originally expensive and difficult, shale gas production is becoming more widespread around the world, largely due to advances in the horizontal drilling and hydraulic fracturing techniques necessary to enable the gas to flow to the surface. Mainly pioneered in the US, where the success of shale gas production has created potential for an LNG export industry.

Ship-or-pay clause

Contract clause requiring payment for the transportation of the natural gas even in case the natural gas is not transported.

Ship’s agent

Person or firm that transacts all business in a port on behalf of shipowners or charterers. Also called shipping agent or agent.


Any gas-market participant that holds a contract to transport gas on a pipeline or local distribution company.

Short-term supplies

Natural gas purchases usually involving 30-day, short-term contract or spot gas.


The reduction in volume of wet natural gas caused by the removal of natural gas liquids, hydrogen sulphide, carbon dioxide, water vapour and other impurities from the gas.

Sour gas

Natural gas that contains significant amounts of hydrogen sulphide (usually greater than 16 ppm) and possibly other objectionable sulphur compounds (mercaptans, carbonyl sulphide). Also called acid gas.

Specific gravity

The ratio of the density of a substance to the density of a reference substance, both at specified physical conditions. As applied to gas, air is the reference substance and the physical conditions are a specified temperature and atmospheric pressure.

Spot gas

Natural gas that is available and purchased on a short-term basis and is furnished to customers on an as-available basis.

Spot gas market

Short-term buying and selling of natural gas.

Spot voyage

A charter for a particular vessel to move a single cargo between specified loading port(s) and discharge port(s) in the immediate future.

Standard metering

Base standard conditions, plus agreed corrections, to which all natural gas volumes are corrected for purposes of comparison and payment.


A means of maintaining a reserve of natural gas supplies to meet seasonal demands.

Straddle plant

A gas-processing plant constructed near a transmission pipeline downstream from the fields where the natural gas in the pipeline has been produced.

Stranded gas

Gasfield located in area where there are no transportation services or markets within any economically reasonable distance. See Remote gas


A party that sells a commodity (for example, natural gas).

Suspended gas discovery

A gasfield identified by a discovery well, but not being produced or developed.

Swap (derivatives market)

Swaps are instruments that allow a trader to exchange a fixed price futures contract with a floating price contract. Increasingly regarded as useful in the LNG futures market as a Hedging mechanism.

Swap (physical LNG market)

A swap can refer to an exchange of delivery contracts, so that, for example, LNG contracted to go to destination A goes instead to destination B, while gas from elsewhere originally contracted to go to destination B now goes to destination A.

Sweet gas

Natural gas that contains such small amounts of hydrogen sulphide (and other sulphur compounds) and carbon dioxide that it can be transported or used without purifying, with no deleterious effect on piping and equipment.

Swing gas

Natural gas bought on short notice to meet unexpected daily demands not covered under long-term contracts.

Synthetic natural gas (SNG)

Methane obtained from sources other than naturally occurring reservoirs of natural gas, such as by crushing and gasifying coal at high temperature, refining heavier hydrocarbons, or processing rubbish or other organic materials. Gases other than natural gas or liquid or solid hydrocarbons converted to a gaseous fuel of heat content, compatibility and quality equivalent in performance to that of natural gas. Also known as Syngas.

System capacity

The physical limitation of a gas pipeline or storage system to flow gas to end-users. Also called normal system capacity.

System supply

Natural gas supplies purchased, owned and sold by the supplier.