addressing uncertainty in oil and natural gas industry greenhouse

Appendix F
UNCERTAINTY ESTIMATION DETAILS FOR AN EXAMPLE INVENTORY
As stated in Section 5.0, this Appendix provides the source-by-source calculation and aggregation of
uncertainty for a hypothetical facility. 7
The following summarizes the characteristics of the onshore oil field example facility introduced in
Section 5. This example field is described in detail in the API Compendium (API, 2009). The calculation
exhibits that are reprinted directly from the API Compendium but have additional uncertainty information
added, are indicated by the highlighted text. Excerpts of Tables 5-1 and 5-2 are provided to reiterate
information used in the uncertainty calculations.
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 from
the eGRID subregion ERCOT all annually. The facility gas composition is presented in Table F-1 and
results in a heating value of 928 Btu/scf with an uncertainty of ±4%, based on engineering
judgment.
Table F-1. Gas Composition for Onshore Production Platform
(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.
7 Note, the calculations shown in this Appendix are rounded to three significant figures. Actual calculations were
compiled in a spreadsheet with rounding reserved for the final results.
Pilot Version, September 2009 F-1