Our Industry's Journey in Measuring Methane Emissions and Where We'reGoing from Here

摘要

The International Association of Oil and Gas Producers(IOGP)has collected environmental data from itsmember companies every year since 1999.The objective of this programme has been to allow membercompanies to compare their performance with other companies in the section,with the aim to leadto improvement and more efficient performance.It also contributes to the industry's wish to be moretransparent about its operations(IOGP,2017).There is growing attention to methane emissions from the oil and gas industry supply chain.Naturalgas operations contribute to global anthropogenic methane emissions and if not properly managed mayundermine the widely recognized environmental benefit of gas utilization.Nevertherless,statistics formethane emissions,particularly from O&G sector,are widely variable.This is not only a risk for climatechange mitigation,but also financial and regulatory risk for both investors and operators.In 2017,the Environment Data Subcommittee held a workshop to share and discuss the technical aspectsof methane emissions data measurements,collection and reporting.As a result,a dedicated task force(TheMethane Reporting Task Force)was created to: 1.Improve the level of accuracy and credibility of IOGP members'reported methane data into theIOGP annual EPI reporting process.2.Provide IOGP members with practical operational guidance for estimation and accounting methaneemissions,together with a related level of confidence/accuracy,that would provide improvedclarity for the IOGP EPI reporting process.As part of this aim,the IOGP task force has undertaken a study comparing the different methaneemissions estimation methodologies and emissions factors for upstream oil and gas operations acrossdifferent regulator and countries including the United Kingdom,Norway,Netherlands,the United StatesEnvironmental Protection Agency,and Australia.The objective of this paper is to identify the main factors of variability within current emissions estimatesand look for potential consequences on defined boundaries and standardized common methodologiesthroughout O&G operations.Even though the basis for reporting emission categories is similar,there are key differences observed inreporting scope,definition of business sectors,particularly for the onshore gas sector,granularity of sourcedefinition,and the emissions factors.With respect to the main contributive categories of emissions of the methane inventories,and consideringthe respective national specific gas compositions: 1.Cold venting is determined in all countries based on vent rate measurement,mole fraction and timeduration.This is the same as recommended by API Compendium 5.3.Little difference is to beexpected between the countries.2.Fugitive leaks are estimated by all countries on the basis of either Optical Gas Imaging(OGI)leak/noleak approach or emission factors by major equipment/sources.The difference is that some countriesuse an API EF,the UK a local EF,and the US the EPA EF.A comparison for all the different potentialsources versus API,Local or EPA EF has not been conducted,as this was considered out of scopeof this study and of limited benefit.3.Flaring design efficiency use mainly standards from 98% to 99% 4.Large variations,up to a factor of 20-30,are noticed between the combustion emission factors(EF)for gas turbines and gas engines used in the various countries,which may result in(relative)over/under reporting of emissions in this category.The contributions of combustion sources are small compared to overall CO2-e emissions so the totaldifference may not be so large(<1%).However,the result of these EF variations could be particularlysignificant for combustion of gas in gas engines and flares,where relevant.Those differences that exist between countries may result in differences for CH4 reporting.The report mayhelp companies operating in different countries understand that there will be differences across countries in: 1.Reporting scope: own generated emissions.2.Business secto