U.S. Environmental Protection AgencyNatural Gas STAR Program

Optimize Separator Operating Pressures to Reduce Flash LossesSPE Paper 94373

B. Boyer - COMM Engineering &S. O'Connell, Devon Energy Corp.

Outline

Introduction Introduction Flash LossesFlash LossesOpportunityOpportunityMethods UsedMethods UsedConclusions Conclusions

Introduction

STAR BMPs examples of Optimization STAR BMPs examples of Optimization Many opportunities existMany opportunities existMany solutions neededMany solutions neededFlash gas from separators and storage Flash gas from separators and storage

tanks are natural gas producttanks are natural gas product

Flashing Losses

Flashing losses result from oil pressure Flashing losses result from oil pressure drops during the separation processdrops during the separation process

Flash gas routinely vented to the Flash gas routinely vented to the atmosphere or burned in a flareatmosphere or burned in a flare

Sources of flash to atmosphere include Sources of flash to atmosphere include separators, heater treaters, storage tanksseparators, heater treaters, storage tanks

Higher BTU gas from storage tanksHigher BTU gas from storage tanks

Flashing Losses

Intermediate flashIntermediate flashIntermediate pressure separators that send oil Intermediate pressure separators that send oil

to low pressure separator or heater treaterto low pressure separator or heater treaterComputer simulationsComputer simulationsFixed roof atmospheric storage tanksFixed roof atmospheric storage tanksPipeline pigging operationsPipeline pigging operationsGas plant inlet separators dumping to storage Gas plant inlet separators dumping to storage

tankstanks

Typical Flash Destination

Optimization Opportunity

Minimize operating pressure of low-Minimize operating pressure of low-pressure separators that dump to storage pressure separators that dump to storage tanks to reduce flash losses tanks to reduce flash losses Results in decreased gas vented by Results in decreased gas vented by storage tanks and increased gas to salesstorage tanks and increased gas to salesMinimal cost to implement with Minimal cost to implement with immediate paybackimmediate payback

Why Optimize Separators?

Easy, inexpensive to increase profits Easy, inexpensive to increase profits Gas STAR Program reportingGas STAR Program reportingConserves natural resourcesConserves natural resourcesGreenhouse Gas emission creditsGreenhouse Gas emission creditsReduce volatile organic compounds (VOC)Reduce volatile organic compounds (VOC)Reduce benzene and other hazardous air Reduce benzene and other hazardous air

pollutant emissionspollutant emissions

Devon Energy Corp. Case Study

Surveyed facilitiesSurveyed facilitiesChose G.A. Ray No. 93 FacilityChose G.A. Ray No. 93 FacilityOptimize separator pressures to increase Optimize separator pressures to increase

gas to sales minimal costsgas to sales minimal costsField cooperation – sampling, optimization Field cooperation – sampling, optimization

options, implementationoptions, implementation

Method

Step1. Choose Flowrate Estimation MethodStep1. Choose Flowrate Estimation MethodStep 2 – Collect Process DataStep 2 – Collect Process DataStep 3 – Determine existing GOR and flash rateStep 3 – Determine existing GOR and flash rateStep 4 – Determine and implement optimal Step 4 – Determine and implement optimal

operating pressuresoperating pressuresStep 5 – Determine new GOR and flash rate after Step 5 – Determine new GOR and flash rate after

lowering operating pressureslowering operating pressuresStep 6 – Calculate the reduction in vent gas and Step 6 – Calculate the reduction in vent gas and

the monetary value of the vent gasthe monetary value of the vent gas

Additional Solution

Install vapor recovery after optimization when Install vapor recovery after optimization when adequate amount of gas ventedadequate amount of gas vented

See Natural Gas STAR’s Lessons Learned See Natural Gas STAR’s Lessons Learned document: “Installing Vapor Recovery Units on document: “Installing Vapor Recovery Units on Crude Oil Storage Tanks” Crude Oil Storage Tanks” (www.epa.gov/gasstar)(www.epa.gov/gasstar)

Conclusions

Methane emissionsMethane emissionsBefore optimization = 653,000 scf/yearBefore optimization = 653,000 scf/yearAfter optimization = 317,000 scf/yearAfter optimization = 317,000 scf/yearIncreased potential net to sales = 336,000 Increased potential net to sales = 336,000

scf/yearscf/yearIncrease profits to approx. $7000/yearIncrease profits to approx. $7000/year

Devon reporting this data to Gas STAR ProgramDevon reporting this data to Gas STAR Program