addressing uncertainty in oil and natural gas industry greenhouse

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formed, as shown in API Compendium Equation 5-9. For this example, the chemical reaction for each compound is: CH 4 : CH 4 + 2H 2 O = 4H 2 + 1CO 2 C 2 H 6 : C 2 H 6 + 4H 2 O = 7H 2 + 2CO 2 C 4 H 10 : C 4 H 10 + 8H 2 O = 13H 2 + 4CO 2 For this approach, the moles of carbon and hydrogen are determined by multiplying the number of molecules of each in each compound by the composition of each compound in the feed gas (i.e., CH 4 , C 2 H 6 , and C 4 H 10 ). These results are used to determine the ratio of moles of carbon to moles of H 2 , and are shown in Table 5-7. Table 5-7. Hydrogen and Carbon Composition Data Compound # C Atoms # H 2 Molecules Concentration Combined Uncertainty (rel) (mole%) Moles C Moles H 2 CH 4 1 4 0.85 5.00% 0.85 3.4 C 2 H 6 2 7 0.08 5.22% 0.16 0.56 C 4 H 10 4 13 0.03 6.01% 0.12 0.39 Total Moles 1.13 4.35 Sum uncertainty (abs) 0.0439 0.0439 Sum uncertainty (rel) 3.89% 3.89% The carbon-to-hydrogen ratio is calculated by dividing the total moles C by the total moles H 2 (1.13/4.35 = 0.26). Since each mole of carbon produces 1 mole of CO 2 , the CO 2 /H 2 ratio is the same as the C/H 2 ratio (0.26). The uncertainty associated with the total moles of C and H 2 is calculated by applying Equation 4-4, using the absolute uncertainties of each molar compound. ∑ 2 U ( abs) = U ( abs) ( C) mole C ∑ mole U ( abs) = (0.0500× 0.85) + (0.0522× 0.08) + (0.0601× 0.03) ∑( mole C) U ( abs) = 0.0439 ∑( mole C) 0.0439 Urel ( ) = × 100% = 3.89% ∑( mole C) 1.13 ∑ 2 2 2 2 U ( abs) = U ( abs) ( H H 2 ) mole ∑ mole 2 U ( abs) = (0.0500× 3.4) + (0.0522× 0.53) + (0.0601× 0.39) ∑( mole H 2 ) U ( abs) = 0.1742 ∑( mole H 2 ) 0.1742 Urel ( ) = × 100% = 4.00% ∑( mole H 2 ) 4.35 2 2 2 Pilot Version, September 2009 5-17
The CO 2 emissions are calculated using Equation 5-9: 6 10 scf H2 lbmole H2 lbmole gas 1.13 lbmole CO2 44 lb CO2 tonne E CO = 13,000 × × × × × 2 year 379.3 scf 4.35 lbmole H lbmole gas lbmole CO 2204.62 lb 2 2 E = 177,700 tonnes CO /yr CO2 2 The CO 2 uncertainty is then calculated by applying Equation 4-6 and using the relative uncertainty values. Urel ( ) = Urel ( ) + Urel ( ) + Urel ( ) Urel CO 2 2 2 2 2 ( ) CO = 15 + 3.89 + 4 = 16.0% 2 2 2 2 Feedstock rate moles C moles H Based on the assumptions applied for the H 2 plant emission methodologies, the uncertainty associated with each of the methods provided in the API Compendium is comparable. In both equations, the aggregated uncertainty is influenced primarily by the ±15% uncertainty values assigned to the feedstock rate (used in the first method) and the H 2 production rate (used in the second method). 5.4 Strategic Reduction of Uncertainty This section addresses the potential need to refine the emission inventory to reduce the uncertainty in the overall emission estimate. There may be several reasons to do this. In some specific locations, there may be state or national regulations, or guidelines for voluntary programs that suggest or require an emission inventory to have uncertainties lower than a certain percentage level. A company may also independently wish to refine its own uncertainty limits, if it considers the uncertainties too large. The reader should note that none of the strategies mentioned here are aimed at reducing the actual emissions of GHGs. That is a separate subject, and while emission reductions are achievable in some cases, they are beyond the scope of this report. This section focuses on reducing the mathematical and statistical uncertainty associated with an existing emission inventory. Once a decision has been made to refine and reduce the uncertainty associated with a given inventory, some strategic analysis of the major sources contributing to the uncertainty is in order. It is important to know which sources significantly contribute to the overall inventory. It would make little sense to refine a term with large confidence bounds, but that contributed very little to the overall inventory. It may also be useful to have a target uncertainty in mind. For example, if the current total uncertainty is ±50.0 % and the company wishes to reduce it to ±25.0%, then that target is useful in the analysis. As uncertainties of individual values in the calculations are examined, values that have uncertainties that are already at or below the 25.0% target, Pilot Version, September 2009 5-18
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Prepared by the LEVON Group, LLC an
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Table of Contents SECTION Page FORE
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List of Tables SECTION Page 2-1 Ove
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FOREWORD The global oil and natural
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DOCUMENT AT A GLANCE This document
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1.0 INTRODUCTION Policymakers use e
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The Intergovernmental Panel on Clim
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2.0 SOURCES OF UNCERTAINTY There ar
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Table 2-1. Overview of Methods Used
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the uncertainty associated with cur
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d. Data processing uncertainty Typi
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d. Material Balance For some emissi
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3.0 OVERVIEW OF MEASUREMENT PRACTIC
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3.1 Flow Measurement Practices Cont
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All these factors should be assesse
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Table 3-1. Example of FFMS Combined
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3.2 Uncertainties of Flow Measureme
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Table 3-3. Compilation of Specifica
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EXHIBIT 3-3: FACTORS TO CONSIDER WH
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3.3.2 Quantifying Sampling Precisio
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Table 3-4. Summary of Selected Carb
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3.5 Heat Content Determination The
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3.5.2 Computational Methods Heating
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using standard methods, non-standar
Page 49 and 50: 0.6 0.4 0.2 Error 0 -0.2 -0.4 -0.6
Page 51 and 52: s ± t × (Equation 4-1) n where s
Page 53 and 54: 4.2.1 Propagation Equations There a
Page 55 and 56: For two terms that might be correla
Page 57 and 58: EXHIBIT 4-1: Uncertainty Example fo
Page 61 and 62: Further guidance for assigning unce
Page 63 and 64: 4.4 Quantifying Measurement Uncerta
Page 69 and 70: Are the data based on a single poin
Page 71 and 72: Two methods are compared. The first
Page 73 and 74: . EXHIBIT 4-6: Uncertainty Example
Page 77 and 78: Table 4-13 shows the uncertainty in
Page 79 and 80: Table 4-13. Comparison of Annual Em
Page 81 and 82: • The evolution of activity and e
Page 83 and 84: These guidelines concentrate solely
Page 85 and 86: (Reprinted from the API Compendium)
Page 87 and 88: Table 5-2. Onshore Oil Field (High
Page 89 and 90: associated with them are assigned b
Page 91 and 92: Table 5-4. Onshore Oil Field (High
Page 93 and 94: 5.2.4 Propagating Assymetric Uncert
Page 95 and 96: U( rel) = U( rel) + U( rel) + U( re
Page 97 and 98: Coke burn rate approach (Equation 5
Page 99: Wt% C ∑ lbmole x lbmole C 12 lb C
Page 103 and 104: GHG Emissions, tonnes/yr 60,000 50,
Page 105 and 106: vast majority of the uncertainty fo
Page 107 and 108: 6.0 REFERENCES AGA, 2008, Greenhous
Page 109 and 110: The Alberta Energy and Utilities Bo
Page 111 and 112: Appendix A GLOSSARY OF STATISTICAL
Page 117 and 118: APPENDIX B LIST OF INDUSTRY MEASURE
Page 119 and 120: Chapter 2.8B Establishment of the L
Page 121 and 122: Chapter 11.5.3 Chapter 12.1.1 Chapt
Page 123 and 124: Chapter 19.4 Chapter 20.1 RP 85 RP
Page 125 and 126: ISO 8222:2002 ISO 8697:1999 ISO 902
Page 127 and 128: ISO 7194:2008 Measurement of fluid
Page 129 and 130: ASTM D4292 ASTM D4892 ASTM D5002 AS
Page 131 and 132: APPENDIX C OPERATING CONDITIONS, IN
Page 133 and 134: Appendix C OPERATING CONDITIONS, IN
Page 135 and 136: Appendix D SELECT MEASUREMENT METHO
Page 137 and 138: c. ASTM UOP539-97, Refinery Gas Ana
Page 139 and 140: interference between known componen
Page 141 and 142: maintained over the room temperatur
Page 143 and 144: APPENDIX E UNITS CONVERSION
Page 145 and 146: − Gasoline density (average) = 0.
Page 147 and 148: Appendix F UNCERTAINTY ESTIMATION D
Page 149 and 150: The uncertainty for the heaters/reb
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∑ 2 U ( abs) = U( abs) ∑(Wt%C)
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Combining the fuel usage for the tw
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Uncertainty Estimate of CO 2 e Emis
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U ( abs) = ( U ( abs) + U ( abs) +
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E E CO2e 219 tonne CO ⎛ 2 0.0108
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E CO 2 6 500× 10 scf gas lbmole ga
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• Fuel Economy (miles per gallon)
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Upper: U ( abs) = (U( abs) +U( abs)
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default CH 4 content is 5.53% from
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Uncertainty Estimate of CO 2 e Emis
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( ) Urel ( ) = Urel ( ) = Urel ( )
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Uncertainty Estimate for CH 4 and C
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specific mole % for CH 4 and CO 2 i
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E CO2 0.07239 tonne CH 4 tonne mole
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U ( rel) = U( rel) +U( rel) +U( rel
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Table F-14. Fugitive Emission and U
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U ( abs) = (U( abs) +U( abs) +U( ab
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Table F-15. Onshore Oil Field (High
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