Measurement Glossary

Discover key measurement terms and definitions.

Organizations and Standards

AER

Alberta Energy Regulator

AGA

American Gas Association

ANSI

American National Standards Institute

API

American Petroleum Institute

ASTM

American Society for Testing and Materials

BCER

BC Energy Regulator

EIA

U.S. Energy Information Administration

FERC

Federal Energy Regulatory Commission

GPA

Gas Processors Association

Measurement Canada

Measurement Canada

NIST

National Institute of Standards and Technology

Saskatchewan Energy Regulator

Saskatchewan Energy and Resources

Measurement Terms

Absolute Pressure

Pressure above that of a perfect vacuum; the sum of gauge and atmospheric pressure (designated by psia).

Acid Gas

Gas having a significant content of hydrogen sulfide, also referred to as Sour Gas.

Allocation

The process of determining ownership rights to the gas delivered to a meter.

API Gravity

An inverse ratio of the density of oil to a relative density (i.e., water). It is used to compare densities of hydrocarbon liquids and often as a measure of quality.

As Delivered Btu

The number of BTUs contained in a cubic foot of natural gas adjusted to reflect the actual water content of the gas at delivered pressure, temperature, and gravity conditions.

Balancing Agreement

A contractual agreement between two or more legal entities to account for differences between measured quantities and the total confirmed nominations at a point.

Base Density

The density of a fluid, reported at legal pressure and temperature base.

Beta Ratio

The measured bore diameter of an orifice plate divided by the measured internal diameter of the meter tube; this ratio should be in the range of 0.20 to 0.60 for minimum uncertainty in measurement.

BTU (British Thermal Unit)

A unit of measurement for energy, representing the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit.

Combined Correction Factor (CCF)

Factor that can be multiplied against the indicated volume to get the Gross Standard Volume (GSV).

Contract Hour

The time designated by a gas sales contract for the beginning of a new “Contract Day” or “Gas Day.”

Correlation Factor (CF)

A factor used to compensate for the inherent inaccuracy associated with calculating volumes from averages of the flowing parameters as opposed to the actual instantaneous values used by the original flow-computing device.

Cricondentherm

The highest temperature at which two phases (liquid and vapor for most processes) can coexist.

Dekatherm

Ten therms or one million British thermal units (Btu).

Extraction Loss

The extraction of gas plant liquids constituents such as ethane, propane, normal butane, isobutane, and natural gasoline.

Full Well Stream

Well stream gas that has not had separable liquids removed, such as water, oil, or condensate.

Gauge Pressure

Measurement of the amount that the pressure is greater than atmospheric pressure (designated by psig).

GPM (Gallons Per Thousand Cubic Feet)

The quantity of liquefiable hydrocarbons contained in one thousand cubic feet of gas.

Hydrocarbon Dew Point

The temperature at which liquid hydrocarbons condense out of the gas stream.

In-Kind (Take In-Kind)

The taking by an owner of its share of gas or liquids for separate marketing or disposition.

K-Factor

The number of pulses generated by a meter per unit of (nominal) volume.

Keep Whole

Provision in gas processing agreements that allows the producer to receive at least an amount equal to proceeds the producer would have been entitled to had he sold the gas at the wellhead without processing.

Nominations

A request for a physical quantity of gas under a specific purchase, sales, or transportation agreement or for all contracts at a specific point.

Reid Vapor Pressure

The pressure measured when performing a Reid Vapor Pressure test.

Super compressibility Factor

A factor used in a volume measurement calculation to correct for deviation from the ideal gas law in differential meters.

Tap Location

This identifies which tap is used to measure line pressure. It may be measured either upstream or downstream.

Tap Type

The location of the taps on either side of the orifice plate across which the differential pressure is measured.

Thermowell

A closed-end reentrant tube designed for insertion of a temperature-sensing element and provided with means for pressure-tight attachment to a vessel.

Time Leads Data / Time Trails Data

Flow computers log averages and accumulate flow over a time interval.

Transmitter/Transducer

A device that converts a signal from a sensor into a form suitable for propagating the measurement information from the site of measurement to the location where the signal is used.

Turn Down Ratio

A term that refers to the operational range of a device and is defined as the ratio of maximum capacity to minimum capacity at a stated measurement uncertainty.

Vacuum

Measurement of the amount that the pressure is less than atmospheric pressure.

Vapor Pressure

The Equilibrium Vapor Pressure (EVP) at a given temperature and pressure.

Wobbe Index

A measure of the interchangeability of gaseous fuels, quantifying the energy output.