GPA Standard # 2172-09 Composition Based Calculation of Natural Gas Properties - October 2010
GPA Standard # 2172-09
Composition Based Calculation of Natural Gas Properties
Water vapor is a zero heating value component of undehydrated natural gas streams. Because it affects the value of such gas deliveries, the publication of a standard addressing how to treat the presence of water vapor has long been needed. GPA 2172-09 is the domestic natural gas industry's standard for calculating gas properties for custody transfer measurement based on chromatographic gas analysis. This standard addresses how to use the water vapor content in determining the real gas properties - i.e., relative density, Btu content, and hydrocarbon liquid content (GPM). The standard includes methods for calculating "As-Delivered Btu" and "Equivalent Dry Volume." Because water vapor is difficult to precisely measure, the standard requires identification of the method used to determine the water vapor content of the gas.
Implementation of this standard is currently scheduled for January 2011; however, many industry experts anticipate delays due to the rigorous requirements of implementing this standard where contracts allow. The bottom line: be sure to review the measurement and quality section of your contract(s) to determine if this GPA standard should be applied. It's also worth noting that if the delivery contract is a "Dry or Saturated at base conditions" agreement, the water vapor portion of the contract will not apply in most cases.