addressing uncertainty in oil and natural gas industry greenhouse

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EXHIBIT 4-5: Uncertainty Example for Multiple Flow Measurements, continued Table 4-7. Uncertainty in Summation of Flow Measurements - Annual Assigned Context Specific Uncertainty, % Annual Measurement Total Uncertainty (absolute), 10 3 scf Annual Measurement Flow Rate Uncertainty, % 10 133,947 11.28% 25 303,257 25.54% 100 1,189,036 100.14% As with the annual volume, the uncertainties associated with the meter (1.5%), the context-specific factors (assigned 10%, 25%, and 100% to examine the sensitivity of this uncertainty), and bias (5%) apply to the daily readings and monthly totals. Summing the daily flow rates for the monthly totals results in the same relative uncertainties as shown in Table 4-6. Table 4-8 summarizes the absolute uncertainties for the monthly flow rates. Table 4-8. Uncertainty in Summation of Flow Measurements – Monthly Monthly Measurement Flow Rate Uncertainty Relative Uncertainty, % 11.28% 25.54% 100.14% 10% 25% 100% Month MMscf (absolute uncertainties, 10 3 scf) January 83.50 9,419 21,325 83,614 February 78.28 8,830 19,991 78,382 March 107.45 12,121 27,442 107,595 April 103.83 11,712 26,516 103,966 May 104.59 11,798 26,712 104,733 June 102.87 11,605 26,273 103,014 July 100.62 11,351 25,699 100,761 August 106.03 11,960 27,078 106,171 September 104.23 11,758 26,620 104,374 October 102.28 11,537 26,121 102,417 November 98.43 11,104 25,139 98,566 December 95.31 10,752 24,342 95,443 4.4.1 Measurement Uncertainty – Multiple Measurements Continuing with the decision tree provided in Figure 4-4, where multiple measurement points are available, the corresponding uncertainty can be derived on the basis of a statistical sample. See Cochran, 1977 for a comprehensive guide to sampling. Pilot Version, September 2009 4-21
Are the data based on a single point measurement or multiple measurements? Multiple points Do the measurements represent a sampling of the measured parameter? Yes Apply Equations 4-1 through 4-3 to calculate the mean and standard deviation, respectively. Apply Equation 4-8 to estimate the uncertainty based on the measured data, OR apply Equation 4-9 to estimate uncertainty for a single observed estimate where other data is used for to quantify the uncertainty. The sample standard deviation “includes contributions to the precision both from the measurement system and from the material composition variation from sample to sample” (Coleman and Steele, 1989). In other words, if the measured data for an emission source are derived from a statistical sample, the use of the standard deviation as a measure of the spread of the data accounts for uncertainty of the measurement instrument and the differences among the samples. For example, if three samples are taken every month and the data for the 36 samples are used to calculate a yearly mean, the uncertainty calculated from these samples accounts for both the uncertainty in the measurement instrument and the variability among observations. Thus, this uncertainty will be larger than the uncertainty due to measurement error alone. As the sample size increases, the uncertainty that combines the instrument error and context-specific factors will decrease. Next, we would calculate the standard deviation of the sample using Equation 4-1. The IPCC Good Practices document and others recommend applying the Equation 4-8 to quantify the uncertainty of the data set (IPCC, 2001), which is also referred to as the relative expanded uncertainty and can be thought of as half the bandwidth of a 95% confidence interval (ISO, 2005). t× s( x)/ n U( rel)( x) = × 100% (Equation 4-8) x where U(Rel)(x) = the relative expanded uncertainty in the data set (%); t = a value based on Student’s t-distribution with n-1 degrees of freedom which gives a 95% confidence interval; x = is the mean for the set of data calculated in Equation 4-3; s( x ) = the standard deviation of the data set calculated in Equation 4-2; and n = the sample size for the set of data. If one uses a single observation as an estimate and uses other data to calculate the uncertainty, Section A1.2.3 of the IPCC Good Practices document explains that Equation 4-9 should be used instead of Equation 4-8 (IPCC, 2006). IPCC’s example application of this approach is for the use of single emission estimate for a particular year that has been calculated on more than one occasion. The recalculations have Pilot Version, September 2009 4-22
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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
Page 17 and 18: Table 2-1. Overview of Methods Used
Page 19 and 20: the uncertainty associated with cur
Page 21 and 22: d. Data processing uncertainty Typi
Page 23 and 24: d. Material Balance For some emissi
Page 25 and 26: 3.0 OVERVIEW OF MEASUREMENT PRACTIC
Page 27 and 28: 3.1 Flow Measurement Practices Cont
Page 29 and 30: All these factors should be assesse
Page 31 and 32: Table 3-1. Example of FFMS Combined
Page 33 and 34: 3.2 Uncertainties of Flow Measureme
Page 35 and 36: Table 3-3. Compilation of Specifica
Page 37 and 38: EXHIBIT 3-3: FACTORS TO CONSIDER WH
Page 39 and 40: 3.3.2 Quantifying Sampling Precisio
Page 41 and 42: Table 3-4. Summary of Selected Carb
Page 43 and 44: 3.5 Heat Content Determination The
Page 45 and 46: 3.5.2 Computational Methods Heating
Page 47 and 48: 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 67: EXHIBIT 4-5: Uncertainty Example fo
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 and 100: Wt% C ∑ lbmole x lbmole C 12 lb C
Page 101 and 102: The CO 2 emissions are calculated u
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
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Chapter 2.8B Establishment of the L
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Chapter 11.5.3 Chapter 12.1.1 Chapt
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Chapter 19.4 Chapter 20.1 RP 85 RP
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ISO 8222:2002 ISO 8697:1999 ISO 902
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ISO 7194:2008 Measurement of fluid
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ASTM D4292 ASTM D4892 ASTM D5002 AS
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APPENDIX C OPERATING CONDITIONS, IN
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Appendix C OPERATING CONDITIONS, IN
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Appendix D SELECT MEASUREMENT METHO
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c. ASTM UOP539-97, Refinery Gas Ana
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interference between known componen
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maintained over the room temperatur
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APPENDIX E UNITS CONVERSION
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− Gasoline density (average) = 0.
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Appendix F UNCERTAINTY ESTIMATION D
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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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