Manual of Petroleum Measurement Standards Chapter 14—Natural Gas Fluids Measurement

Section 4—Converting Mass of Natural Gas Liquids and Vapors to Equivalent Liquid Volumes

GPA 8173-17

SECOND EDITION, JUNE 2017

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Contents

Page

1. Scope 1

2. Summary of Method 1

   1. General 1

3. Normative References 1

4. Terms, Definitions, Abbreviations, and Symbols 2

   1. Definitions 2

   2. Acronyms, Abbreviations, and Symbols 2

5. Limitations of the Standard 3

   1. General 3

6. Calculations 3

   1. General 3

   2. Component Volume from Mole Percent 3

   3. Component Volume from Volume Percent 4

   4. Component Volume from Mass Percent 5

7. Example Calculations—Component Volume from Mole Percent (USC) 60 °F 7

8. Example Calculations—Component Volume from Volume Percent (USC) 60 °F 8

9. Example Calculations—Component Volume from Mass Percent (USC) 60 °F 9

10. Example Calculations—Component Volume from Mole Percent (SI) 15 °C 10

11. Example Calculations—Component Volume from Volume Percent (SI) 15 °C 11

12. Example Calculations—Component Volume from Mass Percent (SI) 15 °C 12

13. Example Calculations—Component Volume from Mole Percent (SI) 20 °C 13

14. Example Calculations—Component Volume from Volume Percent (SI) 20 °C 14

15. Example Calculations—Component Volume from Mass Percent (SI) 20 °C 15

Standard for Converting Mass of Natural Gas Liquids or Vapors to Equivalent Liquid Volumes

1. Scope

   
   

   This standard prescribes a method for calculating liquid volumes at equilibrium pressures and at temperatures of 60 °F, 15 °C, and 20 °C from the mass of a natural gas fluid (liquid or vapor) measured at operating conditions, in conjunction with a representative compositional analysis and published values for each component’s molar mass and absolute density.

   
   

2. Summary of Method

   
   

   1. General

      
      

      1. The total mass of a natural gas liquid or natural gas vapor is determined at operating pressure and temperature using a mass measurement system. The total mass is converted to individual component volumes using a representative component analysis.

         
         

      2. The absolute density of pure hydrocarbons in pounds mass per gallon and in kilograms per cubic meter at 60 °F and 15 °C, respectively, as stated in GPA 2145, Table of Physical Properties for Hydrocarbons and Other Compounds of Interest to Natural Gas and Natural Gas Liquids Industries, shall be used.

         
         

         The absolute density of pure hydrocarbons in kilograms per cubic meter at 20 °C, as generated from REFPROP, NIST Standard Reference Database 23, shall be used until such time as GPA 2145 includes this data set. An exception is made for methane, which has a critical temperature of -82.59 °C (190.56 K). The absolute density of 270 kg/m3 for methane at 20 °C has been extrapolated from GPA 2145-09 and

         shall be used for methane at 20 °C until GPA 2145 is updated to include a dataset of absolute densities at 20 °C. Absolute densities at conditions other than those stated in GPA 2145 should be generated from REFPROP, NIST Standard Database 23, or other source(s) as agreed upon by interested parties.

         
         

      3. The examples in this publication illustrate typical components. In actual practice, all the components detected that are representative of the measured product stream should be included in the conversion to equivalent liquid volumes.

         
         

3. Normative References

GPA 2145, Table of Physical Properties for Hydrocarbons and Other Compounds of Interest to the Natural Gas Industry

REFPROP, Reference Fluid Thermodynamic and Transport Properties, NIST Standard Reference Database 23