addressing uncertainty in oil and natural gas industry greenhouse

CO2 Equilvalents, tonnes/yr
90,000
80,000
70,000
60,000
50,000
40,000
30,000
Carbon Dioxide
Methane
Nitrous Oxide
Other GHGs
20,000
10,000
0
Combustion Vented Fugitive Indirect
Emission Source Category
Figure 5-2. Onshore Oil Field: Summary of CO 2 Equivalent Emissions and Uncertainties
Examination of the uncertainties, as shown in the bars on Figure 5-2, or the absolute uncertainty values in
Table F-15, shows that “vented emissions of CH 4 ” are the most significant source of uncertainty, contributing
36,400 CO 2 e tonnes of uncertainty (based on 2600 ±66.5% CO 2 e tonnes) in a total inventory that had only
37,300 CO 2 e tonnes of uncertainty (based on 170,000 ±21.9% CO 2 e tonnes). Carbon dioxide combustion
sources are the next largest contributor of uncertainty, contributing 6,780 CO 2 e tonnes of uncertainty. The
third largest source is CO 2 vented, with 4,420 CO 2 e tonnes of uncertainty (based on 63,600 ±6.95% CO 2 e
tonnes).
Therefore, should the company wish to reduce uncertainty in the GHG emission inventory from this onshore
oil field facility, these categories would be the primary targets for uncertainty reduction. These appear to be
the sources where uncertainty reduction efforts could be effectively spent to refine the inventory and reduce
the uncertainty.
Reduction of Uncertainty in Vented CH 4 Sources
Within vented emissions, there are 10 sources listed in Table 5-8. The highest ranking source, tank flashing
losses, contributes a significant part of the vented emissions (33% of total vented emissions), as well as the
Pilot Version, September 2009 5-21