1、Manual of Petroleum Measurement StandardsChapter 14Natural Gas Fluids MeasurementSection 4Converting Mass of Natural Gas Liquids and Vapors to Equivalent Liquid VolumesGPA 8173-17SECOND EDITION, JUNE 2017Special NotesAPI publications necessarily address problems of a general nature. With respect to
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16、epartment, API, 1220 L Street, NW,Washington, DC 20005, standardsapi.org.iiiContentsPage1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Summary of Method . . . . . . . . . .
17、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 N
18、ormative References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Terms, Definitions, Abbreviations, and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
19、.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.2 Acronyms, Abbreviations, and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20、 . . . . . . . . . 25 Limitations of the Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21、 . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36.2 Component Volume from Mole Percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36.3 Component Volume from Volume Percent . . . . . .
23、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.4 Component Volume from Mass Percent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Example CalculationsComponent Volume from Mole Percent (US
24、C) 60 F . . . . . . . . . . . . . . . . . . . . . . . 78 Example CalculationsComponent Volume from Volume Percent (USC) 60 F. . . . . . . . . . . . . . . . . . . . . 89 Example CalculationsComponent Volume from Mass Percent (USC) 60 F. . . . . . . . . . . . . . . . . . . . . . . 910 Example Calculat
25、ionsComponent Volume from Mole Percent (SI) 15 C . . . . . . . . . . . . . . . . . . . . . . . . 1011 Example CalculationsComponent Volume from Volume Percent (SI) 15 C. . . . . . . . . . . . . . . . . . . . . . 1112 Example CalculationsComponent Volume from Mass Percent (SI) 15 C . . . . . . . . .
26、. . . . . . . . . . . . . . 1213 Example CalculationsComponent Volume from Mole Percent (SI) 20 C . . . . . . . . . . . . . . . . . . . . . . . . 1314 Example CalculationsComponent Volume from Volume Percent (SI) 20 C. . . . . . . . . . . . . . . . . . . . . . 1415 Example CalculationsComponent Volu
27、me from Mass Percent (SI) 20 C . . . . . . . . . . . . . . . . . . . . . . . 15vStandard 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
28、 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 components molar mass and absolute density. 2 Summary of Method 2.1 General 2.1.1 The total mass of a natura
29、l 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. 2.1.2 The absolute density of pure hydrocarbons in pounds mass per gallon and
30、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 a
31、t 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/m3for methane at 20 C has been extrapola
32、ted 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
33、 by interested parties. 2.1.3 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, Tab
34、le 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 2 API STANDARD 14.4 4 Terms, Definitions, Abbreviations, and Symbols 4.1 Definitions 4.1.1 absol
35、ute density The mass of a substance per unit of volume at a specified temperature and pressure. 4.1.2 Equilibrium Vapor Pressure (EVP) The pressure at which a liquid and its vapor are in equilibrium at a given temperature. 4.1.3 molar mass (M) The mass of a substance divided by its amount of substan
36、ce. 4.1.4 mole The amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon 12. 4.1.5 mole fraction The amount of a constituent divided by the total amount of all constituents in a mixture. 4.1.6 mole percent Mole fraction multiplied b
37、y 100. 4.1.7 natural gas liquids Those hydrocarbons liquefied at the surface in field facilities or in gas processing plants. Natural gas liquids include ethane, propane, butanes and natural gasoline. 4.2 Acronyms, Abbreviations, and Symbols For the purposes of this document, the following abbreviat
38、ions and symbols apply. EVP equilibrium vapor pressure lbm pound mass; 1 lbm = 453.59237 grams (exact) M component molar mass; formerly molecular weight Mnullcomponent mass per mole of mixture Mnullnullnullnullnulltotal mass per mole of mixture m total measured mass mnullcomponent mass from total me
39、asured mass mnullnullcomponent mass of mixture mnull nullnullnullnullnulltotal mass of mixture STANDARD FOR CONVERTING MASS OF NATURAL GAS LIQUIDS OR VAPORS TO EQUIVALENT LIQUID VOLUMES 3 NGL natural gas liquid nullnullnullcomponent absolute density SI international system of units (Systeme Internat
40、ionale) USC U.S. customary units of measurement Vnullcomponent volume at base temperature and a reference base pressure of 14.696 psia (101.325 kPa). When the substance is not in the liquid phase at 14.696 psia (101.325 kPa), the reference base pressure is then the equilibrium vapor pressure at base
41、 temperature. vnullcomponent volume fraction of mixture wnullcomponent mass fraction of mixture; formerly weight fraction xnullcomponent mole fraction of mixture i (subscript) ith component null number of components in the mixture 5 Limitations of the Standard 5.1 General 5.1.1 Methods for determini
42、ng total measured mass are not covered by this standard. 5.1.2 Methods for obtaining representative samples and subsequent compositional analyses are not covered by this standard. 6 Calculations 6.1 General 6.1.1 Three methods of calculation are presented, one for each fluid composition unit of meas
43、ure: mole percent, volume percent, and mass percent. The method to use shall correspond with the calibration basis of the instrument used to analyze the fluid. For example, if a chromatograph is calibrated based on volume percent, the method to calculate component volume from volume percent (6.5) sh
44、all be used. 6.1.2 In order to maintain consistent calculation results for accounting purposes, the arithmetic precision of calculations may imply an accuracy exceeding that of the analytical and measurement instruments. It should be noted that intermediate calculations may not represent the actual
45、precision of the results. 6.1.3 A normalization procedure is applied to certain calculations where the summation may differ from the sum of column values for the displayed precision. 6.2 Component Volume from Mole Percent Given the fluid composition as mole percent and the fluid total measured mass,
46、 calculate the component volumes at base temperature and EVP. 4 API STANDARD 14.4 6.2.1 For each component, convert component mole percent values to component mole fraction of mixture (xnull) values by multiplying each component mole percent value by 0.01. 6.2.2 For each component, calculate compone
47、nt mass per mole of mixture (Mnull) to six decimal places by multiplying each component mole fraction (xnull) value by its molar mass (M): nullnull=nullnullnull Eq. (1) 6.2.3 Calculate total mass per mole for the mixture (Mnullnullnullnullnull) by summing the component mass per mole (Mnull) values:
48、nullnullnullnullnullnull=nullnullnullnullnullnullnullEq. (2) 6.2.4 For each component, calculate component mass fraction of the mixture (wnull) value rounded to six decimal places by dividing each component mass per mole (Mnull) value by the total mass per mole (Mnullnullnullnullnull): nullnull=null
49、nullnullnullnullnullnullnullEq. (3) 6.2.5 Normalize the component mass fraction (nullnull) values to total exactly 1.000000. If the sum of the component mass fractions ( nullnullnullnullnullnull) does not equal 1.000000 exactly, adjust the largest component mass fraction so that the sum of the component mass fractions equals 1.000000 exactly. If multiple component mass fractions share the largest component mass fraction value, adjust the largest component mass fraction having the least number of carbon atoms. 6.2.6 Calculate component mass from total meas
