addressing uncertainty in oil and natural gas industry greenhouse

Table 5-2. Onshore Oil Field (High CO 2 Content) Fugitive Emission Sources
(Reprinted from the API Compendium)
Average Component Uncertainty (±%) a
Component
Service
Count
Valves Liquid and Gas 2,740 75
Pump seals Liquid and Gas 185 75
Connectors Gas 110 75
Flanges Liquid and Gas 10,000 75
Open-ended lines Gas 6 75
Others Liquid and 710 75
Footnotes:
Note, the values shown above are for example only. They do not reflect actual operations.
a Uncertainty is based on engineering judgment at a 95% confidence interval.
Facility Description: An onshore oil field in Texas consists of 320 producing oil wells.
Throughput: The average daily oil and gas production rates are 6,100 bbl/day and 30×10 6 scf/day,
respectively.
Operations: The facility operates approximately 343 days per year. The facility imports 917 MW-hr
annually from the eGRID subregion “ERCOT all”. The facility gas composition is presented in Table 5-3
and results in a heating value of 928 Btu/scf with an uncertainty of ± 4%, based on engineering judgment.
Table 5-3. Gas Composition for Onshore Oil Field (High CO 2 Content)
(Reprinted from the API Compendium)
Gas Compound Produced Gas Mole % Uncertainty a
(±%)
CO 2 12 4
N 2 2.1 4
CH 4 80 4
C 2 H 6 4.2 4
C 3 H 8 1.3 4
C 4 H 10 0.4 4
Footnote:
a Uncertainty is based on engineering judgment at a 95% confidence interval.
Note: the values shown above are for example only. They do not reflect average operations.
Most of the GHG emissions from this facility are from combustion sources. A small additional amount
comes from vented sources since the oil field gas contains a relatively high CO 2 content (12 mole %).
In this example, emissions from some emission sources are calculated by use of emission factors, using the
following simple equation:
Pilot Version, September 2009 5-4