Best Practices & Readily AvaTechnologies to Minimize OffPlatform Natural Gas Emissio

Scott C. BartosU.S. Environmental Protection AgDon RobinsonICF InternationalNew Orleans, LAMarch 30, 2011
Agenda

Natural Gas STAR OverviewClimate Benefits of Methane Emissions ReTop Offshore Methane Emissions SourcesVenting vs Flaring: Gas Capture and Control Options

Centrifugal CompressorsReciprocating CompressorsStorage TanksPneumatics

Fugitives: non vent/flare issue Source: Spring 2004 Partner Up
Natural Gas STAR Overview

Voluntary partnership that encourages oil and natural gas companieeffective technologies and practices that improve operational efficieemissions of methane, a potent greenhouse gas and clean energy Over 130 Partners, including 12 International PartnersGas STAR Partners reduced methane emissions by 86 Bcf in 2009 

904 Bcf in cumulative reductions since 1990Company-reported cost-effective projects

904

86

0

100200300400500600700800900

1000

2003 2004 2005 2006 2007 2008 2009

Annual (Bcf)Cumulative (Bcf)

Domestic Natural Gas STAR Methane Reductions

Bcf
Why Focus on Minimizing Methane Losse

Degrees Celsius

Source: Pew Center on Global Climate Change, 2003

-0.8-0.6-0.4-0.2

0

0.20.40.6

SOx

Non GHGs

21002050

CO2

NonCO 2 GHGs

CH4

 In the near te

reduction in gemissions wil

temperature 50% reductiodioxide emiss



2nd most important GHG accounting for ~18% of to

radiative (climate) forcing

 A primary component of natural gas and a valuabl

burning energy source

 Critical to achieving short-term climate protection g
Offshore Emission Reduction Opport

EPA estimates the top 5 emissions sources below account fomethane emissions from offshore operations1Emissions from 4 of the 5 largest sources are vented - remaifugitive emissions (i.e., equipment leaks)

1) Centrifugal Compressor Wet Seal Degassing

o 77.8% of total emissions

2) Vents (e.g., reciprocating compressors, storage tanks, and pn

o 8.7% of total emissions

3) Fugitives

o 7.2% of total emissions

4) Natural Gas Engines

o 3.5% of total emissions

5) Glycol Dehydrators

o 1%

1 Bylin, C., Schaffer, Z., Goel, V., Robinson, D.R., Campos, A., Borensztein, F., “Designing the Ideal Offsh

Mitigation Strategy,” SPE 126964, 2010 SPE International Conference on Health, Safety and Environ

Exploration and Production, Rio de Janeiro, Brazil, April 12-14, 2010. Emission factors used to deve

combine updated EPA information for certain sources with GOADS data to assess 15 large platforms
Wet seals emit gas by design

High pressure seal oil circulates between rings around the compressorshaftLittle gas leaks through the oil sealSeal oil degassing may vent 40 to 200 cubic feet per minute to the atmosphere

Centrifugal Compressor Wet Sea
Replace wet seals with dry seals

At high rotation speeds, gas is pumped between rings creating a high pressure barrier to leakageOnly a small volume of gas escapes through the cf/m per seal)Less O&M costs due to elimination of ancillary e(no seal oil system)

Partner Experience:

Converted 3 compressors to dry seals at a cost $444,000 per compressorReduced emissions by 20,500 Mcf per compresyear3.1 year payback from gas savings alone at $7 

Centrifugal Compressor Dry Sea
Centrifugal Compressor Gas Cap

Capture seal oil degassing vents and route to a fuel ga

Installing a degassing drum at fuel gas pressure allows a large gas dissolved in the seal oil to flash and be routed to a fuel gas Additional equipment includes a degassing drum, a fuel filter (dpressure regulator.One partner reported implementing this project saving 63 MMcfInstallation cost estimated to be $22,000Payback period of 1 month assuming $7 per Mcf
Rod packing leaks gas by design

Newly installed packing may leak 60 cubic feet (cf/hour) 

Where packing rings are properly aligned and fitted

Worn packing has been reported to leak up to 9

Reciprocating Compressors
Economic replacement of rod packing and rnecessary

Measure rod packing leakage

When 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 back cost

Partner Experience

Reduced Emissions by 950 Mcf per yearCost of packing replacement: $3,000At $7 per Mcf, this replacement pays back in <6 

Reciprocating Compressors
Emissions Source

Flash losses (due to pressure differential)Working and Standing losses

Solutions

Install Vapor Recovery Unit (VRU)Can recover up to 95% of hydrocarbon vapors from tanks

Requirements

Steady source and sufficient quantity of lossesUseful outlet for gas recovered by the VRU

Re-injected into sales pipelineUsed as on-site fuelSent to a processing plant to recover valuable NGLs

Storage Tanks

Vapor R

Courtesy of H
In general, if capturing 25 Mcf/day the payback is 3.3 ymonths if capturing 500 Mcf/day (adjusted for offshore, per Mcf)One partner reported a payout of <1 month (@$5 per Minstalling an EVRUTM with an estimated cost of installat

$75,000.1

1http://www.epa.gov/gasstar/documents/workshops/dallas-2004/installingvaporrecovery.ppt#288,1,I

Recovery Units to Reduce Methane Losses

Storage Tanks
Emissions Source

Process controllers (e.g. pressure, level) bleed pneumatic signcontinuously and during actuationGas bleed may be unnecessarily high

Solutions

Replace or retrofit high-bleed devicesto achieve low-bleed levels (< 6 scfh of natural gas)Replace high-bleed device with a no-bleed device

Requirements

For low-bleed devices: safety with control action

Some equipment may require high bleed devices to operate safely, as is the case with some compressors which require a quick response from pneumatic devices

For no-bleed devices: mechanical, instrument air, electric

Payback periods ranging from <1 month to 14 monthsOne partner reported 2 MMcf per year by installing an instrumsystem on their offshore platformPayback period of 21 months assuming $7 per Mcf (not incluadditional O&M savings, such as supply gas related downtim

FisheContSourc

Pneumatics
Fugitives (i.e., Equipment Leaks)

Not vented emissions, but rather equipment leaks controlled cost-effectivelyLeaks occur from valves, connectors, compressor lines

Open-ended lines, compressor seals, blowdown valves, starters, and pressure relief valves represent <3% of com>60% of fugitive methane emissions

Fugitive losses can be dramatically reduced by ima directed inspection and maintenance (DI&M) pro

Voluntary program to identify and fix leaks that are cost-erepairSurvey cost will typically pay out in the first yearProvides valuable data on leak sources with information look “next time”

Implementation of a DI&M program on offshore plahave been reported by several Partners and resultsignificant savings.1

1 For one example, visit: http://epa.gov/gasstar/documents/workshops/2008-tech-transfer/neworleans4.pdf
Summary – Offshore GHG Emissions Capture and Control Option

It is possible to significantly reduce emissiooffshore facilities through projects such as:

Replacement of centrifugal compressor wet seaseals or capture of seal oil vent gas for fuelReplacement of reciprocating compressor rod pInstalling vapor recovery units on crude oil storReplacement/retrofit of high-bleed pneumatic dachieve low-bleed levelsImplementation of a DI&M program

These projects can yield additional revenuelower operating/maintenance benefits
U.S. EPA Contact Information

Scott C. BartosEPA Natural Gas STARProgram Managerbartos.scott@epa.gov(202) 343-9167

Suzie WaltzerEPA Natural Gas Program Managewaltzer.suzanne@

(202) 343-9544