addressing uncertainty in oil and natural gas industry greenhouse

U ( rel) = U( rel) +U( rel) +U( rel) +U( rel)
2 2 2 2
E CO ,E
2 CH4
AF EF Facility mole% Default mole%
Urel = + + + =+ −
( )
2 2 2 2
( )
E CO ,E
1.00 310 4.00 5.53 310%, 100% tonnes/yr
2 CH4
Because the emissions cannot be less than zero, the lower bound uncertainty value for this emission source
is truncated at 100%. Therefore, separate upper and lower bound uncertainties are estimated for the CO 2 e
emissions.
U ( abs) = (U( abs) +U( abs)
2 2
ECO2e ECO2 ECH4
Upper:
2 2
Uabs ( ) = (3.10× 0.131) + (3.10× 21× 0.318) = 20.7 tonnes CO e/yr
ECO2e
2
20.7 tonnes CO e/yr
Urel ( ) = 100% × =+ 304% tonnes CO e/yr
( )
2
ECO2e
2
6.81 tonnes CO2e/yr
U( abs) = U( abs) + U( abs)
2 2
ECO2e ECO E
2 CH4
Lower: abs ( ) ( )
2 2
U( ) = − 1.00× 0.131 + − 1.00× 21× 0.318 = 6.68 tonnes CO e/yr
ECO2e
2
6.68 tonnes CO e/yr
U( rel) = 100% × =−98.1% tonnes CO e/y
( )
2
ECO2e
2
6.81tonnes CO2e/yr
F.11 Uncertainty in Fugitive Sources - Equipment Leaks
Table F-13 provides fugitive component counts associated with the high CO 2 content onshore oil field
facility. The corresponding average component emission factors are also provided based on the API
average oil and gas production emission factors given in Table 6-14 of the API Compendium for light crude.
Because the emission factors are taken from API 4615, the weight fraction of CH 4 is taken from the
“Generic” weight fraction for light crude give in the API Compendium, Table C-6, which assigns
composition by facility type for an aggregate of all streams associated with that facility. Note that the API
Compendium Table C-6 does not provide CO 2 speciation data; therefore, these emissions are not calculated.
Table F-13. Onshore Oil Field (High CO 2 Content) Fugitive Emission Factors
Average Uncertainty b Component EF, tonnes Uncertainty b
Component Service Component Count % TOC/comp./hr a %
Valves Liquid and Gas 2,740 75.0 1.32E-06 100
Pump Seals Liquid and Gas 185 75.0 3.18E-07 100
Connectors Gas 110 75.0 1.64E-07 100
Flanges Liquid and Gas 10,000 75.0 7.69E-08 100
OELs Gas 6 75.0 1.21E-06 100
Others Liquid and Gas 710 75.0 7.50E-06 100
Footnotes:
a Note that for this example, the TOC weight fraction of the gas stream is not 100%. However, the TOC emissions are not adjusted here since
such an adjustment cancels out when calculating CH 4 emissions as shown in Equation 6-9 of the API Compendium.
b Uncertainty based on engineering judgment at a 95% confidence interval.
Pilot Version, September 2009 F-33