Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Daily average send-out

Total volume of natural gas delivered during a proscribed period of time, divided by the total number of days in the period.

Daily contract quantity (DCQ)

The average daily quantity of natural gas that is contracted to be supplied and taken.

Deadfreight

Space booked by shipper or charterer on a vessel, but not used.

Deadfreight factor

Percentage of a ship’s carrying capacity that is not utilised.

Deadweight tonnage (DWT)

A measure of ship carrying capacity. Refers to the following. 1) the number of metric tonnes (2,204.6 pounds) of cargo, stores and bunkers that a vessel can transport. 2) the difference in weight between a vessel when it is fully loaded and when it is empty (in general transportation terms, the net) measured by the water it displaces when submerged to the deep-load line. A vessel’s cargo is less than its DWT.

Dedicated design-day capacity (DDDC)

The maximum volume of gas dedicated to a customer’s use and based on the maximum number of therms recorded by meter on the most demanding day – typically the coldest day – of the year; expressed as a decimal number. Also known as premise demand factor.

Degree day

A measure of the number of degrees above or below an average temperature on any given day. Can also be used as a measure of temperature variation from the norm over a period. 

Dehydration

The removal of water from a fluid.

Dehydrator

Natural gas processing equipment that removes water vapour. Typically, glycol dehydration units are used to dry gas before it is sent to a gas transmission line. If the gas is to be sent to a cryogenic expander plant or LNG plant, then the gas is typically dehydrated using molecular sieves.

Delivered

A term used in LNG shipping contracts to indicate that the seller is responsible for arranging and transporting the gas, and handling any customs procedures and fees, with title only passing to buyer at the point of delivery. The buyer only pays for the LNG that is landed, regardless of losses due to Boil Off and other factors. May also be known as Ex-Ship. Similar, though not identical, to Cost, Insurance and Freight (CIF). 

Deliverability (LNG ships)

One major aspect of LNG project planning consists of estimating the transportation capacity required, taking into account the time necessary for each function in the chain of events within a typical round voyage of an LNG carrier. A typical delivery calculation for a 137,500-cm LNG carrier might be:

One-way distance (nautical miles) 6,000 

Ship ‘service’ speed (knots) 19 

Sea days (round trips) 26.31

Port days (round trips) 2

Total days in voyage (28.31) 29

Operating days in year 350

Voyages per year 12.07

Ship capacity (net cm) 135,000 

Less heel (cm) 3,000

Discharge quantity (cm) 132,000

Annual delivered quantity (cm) 132,000 x 12.07
= 1,539,103 cm


LNG specific gravity varies depending on gas composition, but is typically about 0.45, therefore, the annual deliverability of the vessel is 0.45 x 1,593,103 = 716,896 tonnes. If the maximum output of the liquefaction train is 3.3 million tonnes a year (mt/y), this would equal a maximum daily production of 10,000 tonnes over the 330-day annual operating period. The deliverability of a 137,500 cm ship is 59,400 tonnes, which means it can cater for a daily production of 2,048 tonnes on this route, or five ships can carry 10,240 tonnes, slightly more than maximum production.

Deliverability

The volume of natural gas that a pipeline or distribution system can supply in a given period normally during a 24-hour period.

Delivery point

Designates the point where natural gas is transferred from one party to another.

Delivery-point operator

The operator responsible for balancing loads and allocating natural gas quantities received at delivery points to parties who have contracted to receive deliveries at the point.

Demand charge

A fixed fee, generally paid monthly, to reserve capacity space in a pipeline, storage, or distribution facility.

Demand forecast

Estimate of the level of energy or capacity that is likely to be needed at some time in the future.

Demurrage

A fee, per day or per hour, agreed to be paid by the charterer or receiver of the cargo, for the detention of a vessel, loading or unloading, beyond the Laytime allowed in the charter party.

Department of Energy (DOE)

The US federal department that manages programmes of research, development and commercialisation for various energy technologies, and associated environmental, regulatory and defence programmes. DOE announces energy policies and acts as a principal advisor to the President on energy matters.

Deregulated gas

Natural gas no longer subject to sales and/or price regulation.

Deregulation

The process of removing restrictive regulations on previously regulated power and utility companies.

Derivatives

Financial instruments such as Futures or Swaps, based on the trade of commodities, including gas and LNG. 

Desulphurisation

Processes by which sulphur and sulphur compounds are removed from gases or petroleum liquid mixtures.

Development agreement (DA)

One of the range of agreements between governments and petroleum-resource developers is the DA or one of its variants – the Development and Fiscal Agreement (DFA) or the Development and Production Sharing Agreement (DPSA).

Dew point

The temperature, at a given pressure, at which a vapour will form a first drop of liquid on the subtraction of heat. Further cooling of liquid at its dew point results in condensation of part or all of the vapour as a liquid.

Disabled ship

A vessel impaired so as to be incapable of proceeding on her voyage.

Discount

An amount agreed between buyer and seller to be subtracted from an existing benchmark.

Dispatch

The regulation of an electrical or natural gas system to provide co-ordinated operation; the sequence in which generating resources are called upon to generate power to serve fluctuating loads.

Displacement gas

1) in pipeline transportation, the substitution of a source of natural gas at one point for another source of natural gas at another point. Through displacement, natural gas can be transported by backhaul or exchange; 2) in natural gas marketing, the substitution of natural gas from one supplier of a customer with natural gas from another competing supplier.

Dissolved gas

Natural gas in solution in oil in the reservoir.

Distribution

The delivery of a utility (natural gas, electricity, water) to a household or business.

Distribution company (gas)

A gas utility that obtains the major portion of its natural gas operating revenues from the operation of a retail gas-distribution system, a gas distributor.

Diurnal storage

Daily storage; refers to short-term or peak storage in pipelines or natural gas holders, as opposed to seasonal storage.

Diversion

The flexible routing of LNG cargoes where gas suppliers will seek to move cargoes to markets. Diversion rights for sellers and buyers in LNG supply contracts create opportunities for physical arbitrage, depending on the correlation of such demand and price variations between regional markets.

Downstream

Commercial gas operations that are closer to the end-user or burner tip, as opposed to upstream, which is closer to production.

Draft

The depth of a ship in the water. The vertical distance between the waterline and the keel, expressed in feet in the US and metres elsewhere. May also be called Draught.

Dry dock

An enclosed basin into which a ship is taken for underwater cleaning and repairing. It is fitted with watertight entrance gates which, when closed, permit the dock to be pumped dry.

Dry (or lean) gas

1) gas that has been treated to remove liquids and inerts making it suitable for shipping in a pipeline; 2) natural gas from the well containing no water vapour that will liquefy at ambient temperature and pressure, i.e. the gas is water dry. Gas is usually priced on a dry basis. See Pipeline quality gas; 3) a gas whose water content has been reduced by dehydration or; 4) a gas containing little or no hydrocarbons that could be recovered as a liquid condensate.

Dry gasfield

Reservoir(s) consisting primarily of light hydrocarbons and negligible quantities of condensate.

Dry-measurement basis

Method of measuring total heating value, whereby one cubic foot of gas is measured absent of water vapour under standard conditions of pressure and temperature.

Dual Fuel engines

Engines fitted to some LNG carriers capable of running on either gas from LNG or oil. Running engines on natural gas reduces emissions of carbon dioxide, nitrogen oxide and sulphur oxide 

Downstream pipeline

Pipeline receiving gas from another pipeline at an interconnection point. See Upstream pipeline