Efficient Pigging of Gathering Lines Lessons Learned from Natural Gas STAR Processors Technology...

Efficient Pigging of Gathering LinesEfficient Pigging of Gathering Lines

Lessons Learned from Natural Gas STARLessons Learned from Natural Gas STAR

Processors Technology Transfer WorkshopProcessors Technology Transfer Workshop

Gas Processors Association,Gas Processors Association,Devon Energy, EnogexDevon Energy, Enogex

Dynegy Midstream Services, andDynegy Midstream Services, andEPA’s Natural Gas STAR ProgramEPA’s Natural Gas STAR Program

April 22, 2005April 22, 2005

Reducing Emissions, Increasing Efficiency, Maximizing Profits

AgendaAgenda

Methane Losses from Pipeline PiggingMethane Losses from Pipeline Pigging

Methane RecoveryMethane Recovery

Industry ExperienceIndustry Experience

Is Recovery Profitable?Is Recovery Profitable?

Discussion QuestionsDiscussion Questions


Natural Gas and Petroleum Industry Natural Gas and Petroleum Industry EmissionsEmissions

Processing plants responsible for 36 Bcf of methane Processing plants responsible for 36 Bcf of methane emissions annually, and gathering/ booster stations emissions annually, and gathering/ booster stations contribute >22 Bcfcontribute >22 Bcf

Transmission & Storage Transmission & Storage

98 Bcf 98 Bcf

Production/ Production/ Gathering/ Gathering/ Booster Booster

150 Bcf150 Bcf

Processing Processing 36 Bcf 36 Bcf

Distribution Distribution 73 Bcf73 Bcf

25 Bcf25 Bcf

10 Bcf10 Bcf

18 Bcf18 Bcf

1 Bcf1 BcfOil Downstream Oil Downstream

2 Bcf 2 Bcf

Inventory of U.S. Inventory of U.S. Greenhouse Gas Emissions Greenhouse Gas Emissions and Sinks 1990 - 2002and Sinks 1990 - 2002

EmissionsEmissions

ReductionsReductions


Pigging Gathering LinesPigging Gathering Lines

Hydrocarbons and water condense Hydrocarbons and water condense inside wet gas gathering lines, causing inside wet gas gathering lines, causing pressure drop and reducing gas flowpressure drop and reducing gas flow

Periodic line pigging removes liquids Periodic line pigging removes liquids and debris to improve gas flowand debris to improve gas flow

Efficient pigging:Efficient pigging: Keeps pipeline running continuouslyKeeps pipeline running continuously Keeps pipeline near maximum Keeps pipeline near maximum

throughput by removing debristhroughput by removing debris Minimizes product losses during Minimizes product losses during

launch/capturelaunch/capture

http://www.girardind.com/


Pigging ApplicationsPigging Applications

Pipeline pigs come in a variety of shapes and Pipeline pigs come in a variety of shapes and sizes for different applicationssizes for different applications Cleaning pigs Cleaning pigs

Have brushes or blades to help remove debrisHave brushes or blades to help remove debris Sealing pigsSealing pigs

Make tight seal for removing Make tight seal for removing liquids from the pipeliquids from the pipe

Inspection pigsInspection pigs Specialized pigs outfitted withSpecialized pigs outfitted with

instruments to monitor the instruments to monitor the pipeline integritypipeline integrity

www.westernfilterco.com


Pigging and Methane LossesPigging and Methane Losses

Gas lost when launching and receiving a pigGas lost when launching and receiving a pig

Fugitive emissions from pig launcher/receiver Fugitive emissions from pig launcher/receiver valvesvalves

Gas lost from storage tanks receiving Gas lost from storage tanks receiving condensate removed by piggingcondensate removed by pigging

Gas vented from pipeline blowdownsGas vented from pipeline blowdowns


How Does Pigging Vent Methane?How Does Pigging Vent Methane?

Gathering lines have built-in pig launchersGathering lines have built-in pig launchers Pig launchers have isolation valves for loading pigs, Pig launchers have isolation valves for loading pigs,

pressurizing pigs, and launching pigs with gas pressurizing pigs, and launching pigs with gas bypassed from the pipelinebypassed from the pipeline

Launcher pressuring/depressuring loses methane out Launcher pressuring/depressuring loses methane out the vent valvethe vent valve

Gas FlowGas Flow

Gas FlowGas FlowPig LauncherPig Launcher

Vent ValveVent Valve



Pigging Vents Methane Twice!Pigging Vents Methane Twice!

Methane lost through vent valve on the launcher Methane lost through vent valve on the launcher and again through vent valve on the receiverand again through vent valve on the receiver

Once receiver is isolated from the line, it must be Once receiver is isolated from the line, it must be depressured to remove the pigdepressured to remove the pig

Liquids ahead of the pig drain to a vessel or tankLiquids ahead of the pig drain to a vessel or tank

Isolation valve leaks cause Isolation valve leaks cause excessive venting to excessive venting to depressuredepressure



Estimating Pigging VentsEstimating Pigging Vents

E = P * V / 14.7 * n * fE = P * V / 14.7 * n * f

where:where:E = methane emissions (cubic feet)E = methane emissions (cubic feet)

P = Gathering line pressure (psia)P = Gathering line pressure (psia)

V = Launcher and receiver volume (cubic feet)V = Launcher and receiver volume (cubic feet)

n = % methanen = % methane

f = number of piggingsf = number of piggings

Pig trap isolation valve leakage increases this minimum Pig trap isolation valve leakage increases this minimum amount of gas ventingamount of gas venting


Estimating Emissions from PiggingEstimating Emissions from Pigging

Estimating VEstimating V

Estimating PEstimating P Default: 315 psiaDefault: 315 psia

Line Diameter (inches)Line Diameter (inches) V (cf)V (cf)

66 0.90.9

1212 4.64.6

1818 11.511.5

2626 27.727.7

3434 65.265.2

4848 170.7170.7Adapted from http://www.pigsunlimited.com

Estimating nEstimating n Default: 78.8Default: 78.8


Gas Recovery from Pipeline Condensate Gas Recovery from Pipeline Condensate Storage TanksStorage Tanks

Pressurized condensate collected from pigging Pressurized condensate collected from pigging is sometimes stored in atmospheric tanksis sometimes stored in atmospheric tanks

Gas released during atmospheric flashing can Gas released during atmospheric flashing can be recovered using a vapor recovery unit (VRU) be recovered using a vapor recovery unit (VRU) rather than venting the gasrather than venting the gas

Facilities with existing pigging and liquid storage Facilities with existing pigging and liquid storage capabilities can install an electric or gas capabilities can install an electric or gas powered VRU compressor to recover flashed powered VRU compressor to recover flashed gassesgasses



One partner pigged gathering lines 30 to 40 One partner pigged gathering lines 30 to 40 times per year, collecting several thousand times per year, collecting several thousand barrels of condensate per applicationbarrels of condensate per application

Partner reported saving 21,400 Mcf/yr from Partner reported saving 21,400 Mcf/yr from recovering flash gasesrecovering flash gases

Dedicated VRU was installed with an electric Dedicated VRU was installed with an electric compressorcompressor



Partner reported installation cost of $24,000 for Partner reported installation cost of $24,000 for electric VRU compressorelectric VRU compressor

Annual operating cost of $40,000 mostly Annual operating cost of $40,000 mostly electricityelectricity

Large gas savings and increasing gas prices Large gas savings and increasing gas prices will offset costswill offset costs

Gas Price ($/Mcf) 2.00$ 3.00$ 4.00$ Gas Saved (Mcf/yr) 21,400 21,400 21,400 Annual Savings ($/yr) 42,800$ 64,200$ 85,600$ Installed Cost 24,000$ 24,000$ 24,000$ Operating Cost 40,000$ 40,000$ 40,000$ Payback Period (years) 8.6 1.0 0.5


Use Inert Gases and Pigs to Perform Use Inert Gases and Pigs to Perform Pipeline PurgesPipeline Purges

Pipeline maintenance requires pipe section Pipeline maintenance requires pipe section blowdown before work can beginblowdown before work can begin

Gas in pipeline is usually vented to the Gas in pipeline is usually vented to the atmosphereatmosphere

Inert gas can be used to drive a pig down the Inert gas can be used to drive a pig down the section of pipe to be serviced, displacing the section of pipe to be serviced, displacing the natural gas to a product line rather than natural gas to a product line rather than ventingventing

Inert gas is then blown down to the Inert gas is then blown down to the atmosphere, avoiding methane lossatmosphere, avoiding methane loss


Inert Gas SetupInert Gas Setup

Existing pig launcher can be used, set up to Existing pig launcher can be used, set up to work with inert gaseswork with inert gases

Portable nitrogen supply connected to the pig Portable nitrogen supply connected to the pig launcher ventlauncher vent

Close valve on the main pipeline, pressurize Close valve on the main pipeline, pressurize launcher with inert gas, open launcher tolauncher with inert gas, open launcher tomain pipelinemain pipeline

Supply nitrogen Supply nitrogen until pig reaches until pig reaches receiverreceiver




One partner reported using inert gas to purge six One partner reported using inert gas to purge six pipelines for maintenancepipelines for maintenance

Gas savings from these applications was 538 McfGas savings from these applications was 538 Mcf These savings correspond to a typical application These savings correspond to a typical application

of:of: 2 miles of 10” diameter pipeline2 miles of 10” diameter pipeline Nitrogen at 280 psiNitrogen at 280 psi



No capital costs with existing pigging facilitiesNo capital costs with existing pigging facilities Labor costs are estimated at eight hours for two Labor costs are estimated at eight hours for two

operatorsoperators Nitrogen costs are roughly $8/McfNitrogen costs are roughly $8/Mcf Increased safety is the primary benefit of this Increased safety is the primary benefit of this

opportunityopportunity Gas savings are a secondary benefit, as the Gas savings are a secondary benefit, as the

labor and nitrogen costs outweigh the gas valuelabor and nitrogen costs outweigh the gas value


Discussion QuestionsDiscussion Questions

What opportunities do you have to reduce What opportunities do you have to reduce methane emissions from your pigging methane emissions from your pigging operations?operations?

How can this presentation be made more How can this presentation be made more useful to help you identify and evaluate useful to help you identify and evaluate opportunities?opportunities?

What are the barriers to your implementing the What are the barriers to your implementing the technologies and practices in this technologies and practices in this presentation?presentation?

Efficient Pigging of Gathering Lines Lessons Learned from Natural Gas STAR Processors Technology...

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