1Best Practices & Readily AvailableTechnologies to Minimize OffshorePlatform Natural Gas EmissionsScott C. BartosU.S. Environmental Protection AgencyDon RobinsonICF InternationalNew Orleans, LAMarch 30, 20112AgendaNatural Gas STAR OverviewClimate Benefits of Methane Emissions ReductionsTop Offshore Methane Emissions SourcesVenting vs Flaring: GasCapture and Control OptionsCentrifugal CompressorsReciprocating CompressorsStorage TanksPneumaticsFugitives: non vent/flare issueSource: Spring 2004 Partner UpdateNatural Gas STAR OverviewVoluntary partnership that encourages oiland natural gas companies to adopt costeffective technologies and practices thatimprove operational efficiency and reduceemissions of methane, a potent greenhouse gas and clean energy sourceOver 130 Partners, including 12 International PartnersGas STAR Partners reduced methane emissions by 86 Bcf in 2009904 Bcf in cumulative reductions since 1990Company-reported cost-effective projects390486010020030040050060070080090010002003 2004 2005 2006 2007 2008 2009Annual (Bcf)Cumulative (Bcf)Domestic Natural Gas STAR Methane Reductions

Bcf4Why Focus on Minimizing Methane Losses?

Degrees CelsiusSource: Pew Center on Global ClimateChange, 2003-0.8-0.6-0.4-0.200.20.40.6SOxNon GHGs21002050CO2NonCO2GHGsCH4In the near term, 50%reduction in global methaneemissions will havesametemperature impactas a50% reduction in carbondioxide emissions2ndmost important GHG accounting for ~18% of totalradiative (climate) forcingA primary component of natural gas and a valuable, cleanburning energy sourceCritical to achieving short-term climate protection goals5Offshore Emission Reduction OpportunitiesEPA estimates the top 5 emissionssources below account for 98% ofmethane emissions from offshore operations1Emissions from 4 of the 5 largest sources are vented - remaining source isfugitive emissions (i.e., equipment leaks)1)Centrifugal Compressor Wet Seal Degassingo77.8% of total emissions2)Vents (e.g., reciprocating compressors, storage tanks, and pneumatics)o8.7% of total emissions3)Fugitiveso7.2% of total emissions4)Natural Gas Engineso3.5% of total emissions5)Glycol Dehydratorso1%1Bylin, C., Schaffer, Z., Goel, V., Robinson, D.R., Campos, A., Borensztein, F., “Designing the Ideal Offshore Platform MethaneMitigation Strategy,” SPE 126964, 2010 SPE InternationalConference on Health, Safety andEnvironment in Oil and GasExploration and Production, Rio de Janeiro,Brazil, April 12-14, 2010. Emission factors used to develop this rankingcombine updated EPA information for certain sources with GOADS datato assess 15 large platforms.6Wet seals emit gas bydesignHigh pressure seal oilcirculates between ringsaround the compressorshaftLittle gas leaks throughthe oil sealSeal oil degassing mayvent 40 to 200 cubic feet perminute to the atmosphereCentrifugal Compressor Wet Seals7Replace wet seals with dry sealsAt high rotation speeds, gas is pumped between the sealrings creating a high pressure barrier to leakageOnly a small volume of gas escapes through the gap (~3cf/m per seal)Less O&M costs due to elimination of ancillary equipment(no seal oil system)Partner Experience:Converted 3 compressors to dry seals at a cost of$444,000 per compressorReduced emissions by 20,500 Mcf per compressor peryear3.1 year payback from gas savings alone at $7 per McfCentrifugal Compressor Dry SealsCentrifugal Compressor Gas CaptureCapture seal oil degassing vents and route to a fuel gas systemInstalling a degassing drum at fuel gaspressure allows a large amount of thegas dissolved in the seal oil to flash and be routed to a fuel gas systemAdditional equipment includes a degassing drum, a fuel filter (demister), andpressure regulator.One partner reportedimplementing thisproject saving 63 MMcfInstallation costestimated to be $22,000Payback period of1 month assuming$7 per Mcf89Rod packing leaks gas by designNewly installed packing may leak 60 cubic feet per hour(cf/hour)Where packing rings are properly aligned and fittedWorn packing has been reported to leak up to 900 cf/hourReciprocating Compressors10Economic replacement of rod packing and rod ifnecessaryMeasure rod packing leakageWhen new packing installed – after wear-in periodPeriodically afterward (e.g. six months)Determine cost of packing replacementCalculate economic leak reductionReplace packing when leak reduction expected will payback costPartner ExperienceReduced Emissions by 950 Mcf per yearCost of packing replacement: $3,000At $7 per Mcf, this replacement pays back in <6 monthsReciprocating Compressors11Emissions SourceFlash losses (due to pressure differential)Working and Standing lossesSolutionsInstall Vapor Recovery Unit (VRU)Can recover up to 95% ofhydrocarbon vapors from tanksRequirementsSteady source and sufficientquantity of lossesUseful outlet for gas recovered bythe VRURe-injected into sales pipelineUsed as on-site fuelSent to a processing plant to recover valuable NGLsStorage TanksVapor Recovery UnitCourtesy of Hy-bon Engineering12In general, if capturing 25 Mcf/day the payback is 3.3 years and 2months if capturing 500 Mcf/day (adjusted for offshore, assuming $7per Mcf)One partner reported a payout of <1 month (@$5 per MMBtu) afterinstalling an EVRUTMwith an estimated cost of installation of$75,000.11http://www.epa.gov/gasstar/documents/workshops/dallas-2004/installingvaporrecovery.ppt#288,1,Installing VaporRecovery Units to Reduce Methane LossesStorage Tanks13Emissions SourceProcess controllers (e.g. pressure, level) bleed pneumatic signal natural gascontinuously and during actuationGas bleed may be unnecessarily highSolutionsReplace or retrofit high-bleed devicesto achieve low-bleed levels (< 6 scfh of natural gas)Replace high-bleed device with a no-bleed deviceRequirementsFor low-bleed devices: safety with control actionSome equipment may require high bleed devices tooperate safely, as is the casewith some compressorswhich require a quick response from pneumatic devicesFor no-bleed devices: mechanical, instrument air, electricPayback periods ranging from <1 month to 14 monthsOne partner reported 2 MMcf per year by installing an instrument airsystem on their offshore platformPayback period of 21 months assuming $7 per Mcf (not includingadditional O&M savings, such assupply gas related downtime)Fisher Differential PressureControllerSource: www.emersonprocess.comPneumatics14Fugitives (i.e., Equipment Leaks)Not vented emissions, but rather equipment leaks that can becontrolled cost-effectivelyLeaks occur from valves, connectors, compressor seals, andlinesOpen-ended lines, compressor seals, blowdown valves, enginestarters, and pressure relief valvesrepresent <3% of components but>60% of fugitive methane emissionsFugitive losses can be dramatically reduced by implementinga directed inspection and maintenance (DI&M) programVoluntary program to identify and fixleaks that are cost-effective torepairSurvey cost will typically pay out in the first yearProvides valuable data on leak sources with information on where tolook “next time”Implementation of a DI&M program on offshore platformshave been reported by severalPartners and resulted insignificant savings.11For one example, visit:http://epa.gov/gasstar/documents/workshops/2008-tech-transfer/neworleans4.pdf15Summary – Offshore GHG EmissionsCapture and Control OptionIt is possible to significantly reduce emissions fromoffshore facilities through projects such as:Replacement of centrifugal compressor wet seals with dryseals or capture of seal oil vent gas for fuelReplacement of reciprocating compressor rod packingInstalling vapor recovery units on crude oil storage tanksReplacement/retrofit of high-bleed pneumatic devices toachieve low-bleed levelsImplementation of a DI&M programThese projects can yield additional revenues andlower operating/maintenance benefitsU.S. EPA Contact InformationScott C. BartosEPA Natural Gas STARProgram Managerbartos.scott@epa.gov(202) 343-9167Suzie WaltzerEPA Natural Gas STARProgram Managerwaltzer.suzanne@epa.gov(202) 343-954416