addressing uncertainty in oil and natural gas industry greenhouse

Equation 4-4 and using the absolute uncertainty values. The uncertainty in the emissions factor for the
dehydrator is 191% from Table 5-2 of the API Compendium and 82.8% for the Kimray pump based on
Table 5-4 of the API Compendium.
U ( abs) = (1.91×0.0052859) +(0.828×0.01903) =0.0187 tonnes CH /10 scf
2 2 6
Emission factors 4
6
0.0187 tonnes CH
4
/10 scf
Emission factors 6
4
0.024326 tonnes CH
4
/10 scf
6
( )
Urel ( ) =100%× = ± 77.0% tonnes CH /10 scf
E
30×
10 scf 343 day
0.80 tonne mole CH (facility) 0.024326 tonne CH
6
4 4
CH
= × × ×
4
6
day gas processed yr 0.788 tonne mole CH
4
(default) 10 scf
E
= 254 tonnes CH /yr
CH4
4
The uncertainty of the emissions can be calculated by applying Equation 4-6 and using the relative
uncertainty values. As noted in Table 5-1, there is no uncertainty associated with the count of equipment.
The uncertainty associated with the volume of gas is 5% and the uncertainty associated with the days of
operation is 2%. The uncertainty in the CH 4 content for the facility gas is 4%. The uncertainty for the
default CH 4 content is 5.53% from the GRI/EPA Methane Study (Shires and Harrison, Volume 6,
Tables A-1, A-2, A-3, 1996), which is provided in Table E-4 of the API Compendium.
U( rel) +U( rel) +U( rel) +U( rel)
Urel ( ) =
+U( ) +U( )
2 2 2 2
Dehydrator units Gas processed Days Facility mole%
emissions 2 2
rel
Default mole%
rel
Emission factors
( )
Urel ( ) = 0 + 5 + 2 + 4 + 5.53 + 77.0 =± 77.5% tonnes CH /yr
2 2 2 2 2 2
emissions 4
Uncertainty Estimate for CO 2 Emissions from Dehydration:
6
30×
10 scf 343 day 0.024326 tonne CH
4
tonne mole CH4 0.80 tonne mole CH
4
(facility)
E
CO
= × × × ×
2
6
day gas processed yr 10 scf 16.04 tonne CH 0.788 tonne mole CH (default)
tonne mole gas 0.12 tonne mole CO 44.01 tonne CO
×
× ×
0.8 tonne mole CH tonne mole gas tonne mole CO
2 2
4 2
4 4
E
=105 tonnes CO /yr
CO2
2
The uncertainty of the CO 2 emissions is calculated by applying Equation 4-6 and using the relative
uncertainty values. As noted in Table 5-1, there is no uncertainty associated with the count of equipment.
The uncertainty associated with the volume of gas is 5% and the uncertainty associated with the days of
operation is 2%. The uncertainty in the CO 2 content for the facility gas is 4%. The uncertainty for the
Pilot Version, September 2009 F-20