Glossary
“A” Terms
Associated Gas: Natural gas that occurs with crude oil reservoirs, either as free gas or dissolved in solution; usually produced with crude oil.
“B” Terms
BCF: An abbreviation for billion cubic feet; unit used to measure large quantities of gas.
BCFD: An abbreviation for billion cubic feet per day; unit used to measure the daily volume of gas produced, stored, transported or consumed.
BCM: An abbreviation for billion cubic meters; unit used to measure large quantities of gas.
BCMD: An abbreviation for billion cubic meters per day; unit used to measure the daily volume of gas produced, stored, transported or consumed.
British Thermal Unit: An energy unit equivalent to the amount of energy needed to raise the temperature of one pound of water 1°F from 58.5°F to 59.5°F under standard pressure of 30 in. of mercury; commonly used for measuring gas and other energy sales quantities.
BTU: An abbreviation for British thermal unit.
Butane: A normally gaseous LPG hydrocarbon extracted from natural gas or refinery gas streams; molecular formula C4H10 .
“C” Terms
CF: An abbreviation for cubic feet.
Compressed Natural Gas (CNG): Highly compressed natural gas stored and transported in high-pressure containers; commonly used for transport fuel.
Cubic Feet: Common unit of measurement of gas volume equivalent to the amount of gas required to fill a volume of one cubic foot under given temperature and pressure conditions.
“D” Terms
Dry Gas (lean gas): Natural gas, mainly methane, which remains after liquid hydrocarbon components have been removed, making it suitable for pipeline shipping, LNG processing or industrial usage.
“E” Terms
Ethane: A normally gaseous NGL hydrocarbon extracted from natural gas or refinery gas streams; molecular formula C2H6.
“G” Terms
Gas to liquids (GTL): A process that converts natural gas into synthetic liquid petroleum products, such as diesel fuel and blending feedstock.
“J” Terms
J: An abbreviation for joules.
Joule: Metric unit of energy used for gas sales, mainly in Europe and Australia.
“L” Terms
Lean Gas: See dry gas.
Liquefied Natural Gas (LNG): Natural gas, mainly methane, that has been cooled to -161.5°C or -259°F and condensed into a transportable colorless and odorless liquid.
“M” Terms
Maximum daily quantity (MDQ): Maximum daily quantity of natural gas contracted by the gas seller to the gas buyer.
Mbtu: An abbreviation for thousand or 10³ Btu.
Mcf: The quantity of natural gas occupying a volume of one thousand cubic feet at a temperature of sixty degrees Fahrenheit and at a pressure of fourteen and seventy-three hundredths pounds per square inch absolute.
Methane: The lightest and most abundant of the hydrocarbon gases, it is the principal component of natural gas and LNG; molecular formula C1H4.
MMcf (MMf3): An abbreviation for a million cubic feet.
MMcfd: An abbreviation for million cubic feet per day.
MT: An abbreviation for million tons.
MTA: An abbreviation for million tons per annum (year).
“N” Terms
Natural gas: Naturally occurring mixture of hydrocarbon gases from underground sources composed mainly of methane (more than 85% in some cases), ethane, propane, butane, pentane and impurities including carbon dioxide, helium, nitrogen, and hydrogen sulfide.
Natural gas liquids (NGLs): Natural gas components that change to liquid phase at surface conditions, including ethane, butane, propane, pentane and other condensates; does not include methane, with remains gaseous at surface conditions.
“P” Terms
Peak Load: Maximum electricity or gas demand during a given 24-hour period or otherwise specified time frame.
Pentane: An NGL hydrocarbon, normally liquid, extracted from natural gas or refinery gas streams; molecular formula C1H4.
“Q” Terms
Quad: An energy quantity of one quadrillion Btu, which is approximately the energy equivalent contained in one trillion cubic feet of natural gas.
“R” Terms
Rabbit: A small plug that is run through a flow line by pressure to clean the line or test for obstructions.
Radiator: A heating unit which transfers heat by radiation to objects within visible range and by conduction to the surrounding air which, in turn, is circulated by natural convection; a so-called radiator is also a convector, but the term radiator has been established by long usage.
Rate: The unit charge or charges made to the customers for natural gas.
Rate adjustment provision: A provision in a tariff which provides for changes in rates or total charges because of changes in specified items of cost, such as fuel price, purchased gas, tax, etc.
Rate base: The investment value established by a regulatory authority upon which a utility is permitted to earn a specified rate of return.
Rate Case: A proceeding before a regulatory commission involving the rates to be charged for a public utility service.
Rate schedule, class: A rate schedule which is applicable to a specific customer class of service.
Rate schedule, cogeneration: A special rate to encourage commercial and industrial customers to use gas-fired cogeneration (generate their own electricity and use the waste heat from this process for thermal requirements).
Rebate program: A DSM program in which the utility offers a financial incentive for the installation of energy-efficient equipment. Non-DSM rebate programs also exist, in which the utility offers an incentive for purposes of gaining market share of a specific end-use.
Retrofit: An investment made in an existing building or facility. May be equipment replacements, equipment add-ons, or shell and equipment improvements.
“S” Terms
Service (service line, service pipe): The pipe which carries gas from the main to the customer's meter.
Service area: A geographic area where a utility provides service, usually under provisions of a franchise, charter or certificate, and subject to special government regulations.
Service Charge: The fee charged a customer by a utility for work on the customer's premises. Also, part of a rate schedule, such as a customer charge; generally does not include any gas.
“T” Terms
Tariff: A gas company schedule detailing the terms, conditions and rate information applicable to various types of natural gas service. This document is filed with and approved by FERC or a state regulatory body.
Tariff gas: Gas purchased by gas distributors from gas pipelines. The term is usually used by natural gas distributors to distinguish gas they purchased from pipelines from gas they purchased directly from producers and had transported.
Tariff Volume: The maximum amount of natural gas which a consumer is entitled to receive during any specified time period. Usually the volume of gas that is subject to a curtailment plan. Also referred to as a contract obligations and entitlements.
Throughput: Total of transportation volumes and tariff sales; all gas volumes delivered.
Tie in: To make a connection to an existing pipeline or piping.
Turbine, gas: An enclosed rotary type of prime mover in which heat energy in steam or gas is converted into mechanical energy by the force of a high velocity flow of steam or gas directed against successive rows of radial blades fastened to a central shaft.
Turn-off: Discontinuance of utility service.
Turn-on: Initiation of utility service.
Turn-on charge: The fee paid by a customer to have his utility service turned on.
“U” Terms
Unbundling: The separation of the various components of gas sales, storage, transmission, delivery and etc. into an ala carte menu of services from which a customer may choose only those desired.
Union: A threaded fitting used to couple two runs of pipe together without having to turn or dismantle either run of pipe.
Utility, gas: A company that is primarily a distributor of natural gas to ultimate customers in a given geographic area.
“V” Terms
Valve: A mechanical device for controlling the flow of fluids and gases; types such as gate, ball, globe, needle, and plug valves are used.
Valve Box: A housing around an underground valve to allow access to the valve and to protect the valve from mechanical damage or the effects of weather.
Valve, shut-off: Stops or valves readily accessible and operable by the consumer, located in the piping system (to shut off individual equipment) or between the meter and gas main to shut off the entire piping system.
Vapor: The gaseous state of a substance as distinguished from permanent gases. A gaseous fluid may be classified as either a vapor or a gas. If it is near the region of condensation, it is called a vapor. If it is well above the region of condensation, it is called a gas. Vapors in general do not follow the ideal gas law, and engineers prefer to use tables and charts based on experimental data when working with vapors. Gases, however, may obey the ideal gas laws over a wide range of temperature and pressure.
Vaporizer: A heat exchange used to return liquid natural gas to a gaseous form and then continue to heat the gas to a temperature at which it can be sent into the distribution system.
Vent: An opening in a tank or other piece of equipment, sealed to prevent escape of material within the equipment at normal pressures but so arranged that it automatically opens to relieve excessive pressure in the equipment. Can be arranged for manual opening to depressure equipment as desired. Also, the relief opening in a pressure regulator, normally open to the atmosphere.
“W” Terms
Water heater efficiency measures: Energy Factor (EF) - A measure of the overall efficiency of a water heater based on its recovery efficiency, standby loss and energy input as set out in the standardized Department of Energy test procedures.
Weatherization: The reduction of air infiltration by methods such as caulking and weatherstripping.
Wellhead: The assembly of fittings, valves, and controls located at the surface and connected to the flow lines, tubing, and casing of the well so as to control the flow from the reservoir.
“Y” Terms
Yield point: The stress at which a material exceeds its elastic limit. Below this stress, the material will recover its original size on removal of the stress. Above this stress, it will not.
“Z” Terms
Zero gas: Gas at atmospheric pressure.
