Compositional
analysis of natural gas expressed as mol% can be converted into gallons per Mcf
(GPM) factors by using the formulas and conversion factors shown in Tables 7, 8
and 9 below.
General
Rule:
a gallon is a gallon regardless of pressure base.
Formula
definitions:
Cf/Mol
= number of cubic feet in a Mol (see Note below)
Gal/#Mol
= gallons per pound Mol
Gal/Mcf
= gallons per Mcf
GPM
= gallons per Mcf
PF
= pressure base to convert from
PT
= pressure base to convert to
Note: The number of
cubic feet in a Mol is pressure base sensitive. The standard per the Gas
Processors Association is 379.49 cubic feet at a pressure base of 14.696.
The formula to convert the standard to a different pressure base is as
follows:
379.49 times (14.696
divided by PT)
| Table 7
– the number of cubic feet per Mol at different pressure bases. |
|
Pressure
Base |
Cf/Mol
Factor |
| 14.65 |
380.68157 |
| 14.696 |
379.49000 |
| 14.73 |
378.61406 |
| 15.025 |
371.18037 |
|
| Table 8
–
the number of gallons per pound Mol by component.
|
|
Component |
Gal/#Mol |
| N2 |
Nitrogen |
4.1513 |
| CO2 |
Carbon
Dioxide |
6.4532 |
| H2S |
Hydrogen
Sulfide |
5.1005 |
| C1 |
Methane |
6.4142 |
| C2 |
Ethane |
10.1259 |
| C3 |
Propane |
10.4327 |
| IC4 |
Isobutane |
12.3859 |
| NC4 |
Normal
Butane |
11.9371 |
| IC5 |
Isopentane |
13.8595 |
| NC5 |
Normal
Pentane |
13.7130 |
| C6+ |
Hexane+ |
16.3920 |
|
| Table 9
–
the number of gallons per thousand cubic feet (Mcf) at various pressure bases by component.
|
|
Component |
Pressure
Base |
|
14.65 |
14.696 |
14.73 |
15.025 |
| N2 |
Nitrogen |
10.9049 |
10.9391 |
10.9644 |
11.1840 |
| CO2 |
Carbon
Dioxide |
16.9516 |
17.0048 |
17.0442 |
17.3855 |
| H2S |
Hydrogen
Sulfide |
13.3984 |
13.4404 |
13.4715 |
13.7413 |
| C1 |
Methane |
16.8493 |
16.9022 |
16.9413 |
17.2806 |
| C2 |
Ethane |
26.5993 |
26.6828 |
26.7445 |
27.2801 |
| C3 |
Propane |
27.4054 |
27.4915 |
27.5551 |
28.1069 |
| IC4 |
Isobutane |
32.5361 |
32.6383 |
32.7138 |
33.3689 |
| NC4 |
Normal
Butane |
31.3573 |
31.4557 |
31.5285 |
32.1599 |
| IC5 |
Isopentane |
36.4070 |
36.5213 |
36.6058 |
37.3389 |
| NC5 |
Normal
Pentane |
36.0222 |
36.1353 |
36.2189 |
36.9442 |
| C6+ |
Hexane+ |
43.0596 |
43.1948 |
43.2948 |
44.1619 |
|
Formulas:
(Mol%
divided by 100) times Gal/Mcf = GPM
[(Mol% divided by 100)
divided by Cf/Mol] times 1000 times Gal/#Mol = GPM
Calculation Examples:
(assumes 11.25
Mol% for ethane (C2) and a pressure base of 14.73).
(11.25% divided by 100)
times 26.7445 = 3.0088 GPM C2
[(11.25% divided by 100)
divided by 378.61406] times 1000 times 10.1259 = 3.0088 GPM C2
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Last
updated on March 27, 2002
