Partner Reported Opportunities (PROs) PRO Fact Sheet No. 501 for Reducing Methane Emissions 

Install Pressurized Storage of Condensate 

Technology/Practice Overview 

Description 

Natural gas production is often 

accompanied by significant amounts of 

water and condensate. The condensate is 

saturated with methane at pipeline 

pressures that range up to 750 psig.

When transferred to atmospheric storage 

tanks, a pressure drop occurs causing 

the methane to flash out. Operators 

often vent this gas to the atmosphere. 

Interstage knockout in multi-stage 

compressors with interstage cooling also 

contains raw natural gas liquids (NGL)

saturated in methane. If transferred to 

atmospheric storage, nearly all the 

methane will flash and vent to the 

atmosphere. 

One partner reported installing

pressurized storage, requiring

pressurized transport of condensate to a 

gas plant for economic recovery of gas

liquids and associated methane, volatile 

organic compounds (VOCs), and 

hazardous air pollutants (HAPs) 

emissions reductions. 

Operating Requirements 

Pressurized storage requires the use of 

pressurized transport vehicles. In 

addition, a blanket gas system would be 

required to maintain tank pressure. 

Pressure relief valves should also be 

calibrated for the specific operating 

conditions of the tank. 

Applicability 

This technology is applicable on all gas 

well and gathering/booster compressors. 

Methane Emissions 

Partners estimate condensate production

of 10 barrels per MMcf of gas production 

Estimated 

Gas Price 

Annual 

Methane 

Savings 

Value of 

Annual

 Gas Savings* 

Estimated 

Implementation 

Cost 

Incremental 

Operating Cost 

Payback 

(months) 

$7.00/Mcf 7,000 Mcf $52,000 $37,500 $2,500 10 Months 

$5.00/Mcf 7,000 Mcf $37,000 $37,500 $2,500 13 Months 

$3.00/Mcf 7,000 Mcf $22,000 $37,500 $2,500 22 Months 

Economic and Environmental Benefits 

Economic Evaluation 

Additional Benefits 

 Reducing VOC and HAP emissions 

 Preventing flashing losses 

Estimated annual methane emission reductions 7,000 Mcf per year per tank 

Methane Savings 

* Whole gas savings are calculated using a conversion factor of 94% methane in pipeline quality natural gas. 

Compressors/Engines 

Dehydrators 

Directed Inspection & 

Maintenance 

Pipelines 

Pneumatics/Controls 

Tanks 

Valves 

Wells 

Other 

Applicable Sector(s) 

Production 

Processing 

Transmission 

Distribution 

Other Related Documents: 

Installing Vapor Recovery Units 

on Storage Tanks, Lessons 

Learned 

Recover Gas During Condensate 

Loading, PRO No. 502 
 

 

 

PRO Fact Sheet No. 501 Continued 

Install Pressurized Storage of Condensate (Cont’d) 

and methane emissions of 250 scf per barrel of 

condensate. The condensate production estimate was 

made using a Hysim computer simulation program. 

Actual gas composition and condensate production will be 

unique to each production reservoir. Total partner

reported methane emissions savings were 27,992 Mcf per 

year for 4 installations of pressurized storage tanks. 

Economic Analysis 

Basis for Costs and Emissions Savings 

A methane emissions saving of 7,000 Mcf per year for

each pressure storage installation was reported by the

partner. Savings is based on a 400 barrel pressurized 

tank that stores gas liquids containing 250 scf of 

methane per barrel of condensate. 

The capital cost, including installation, was reported to

be $37,500 in 1998. The operating costs are estimated at

$2,500 for an operator to assist in loading tank trucks for

100 hours annually, since this type of system would be 

more complex than loading from an atmospheric storage 

tank. 

Discussion 

By installing pressurized storage of condensate, 

operators prevent losses of a valuable product as a result 

of flashing. The primary benefit of installing the 

pressurized storage tanks is to reduce VOC and HAP 

emissions. The savings from recovering methane will

justify the costs over a two-year period. 

The average methane content of natural gas varies by natural gas 

industry sector. The Natural Gas STAR Program assumes the 

following methane content of natural gas when estimating 

methane savings for Partner Reported Opportunities. 

Production 79 % 

Processing 87 % 

Transmission and Distribution 94 % 

Methane Content of Natural Gas 

EPA provides the suggested methane emissions estimating methods contained 

in this document as a tool to develop basic methane emissions estimates only. 

As regulatory reporting demands a higher-level of accuracy, the methane emission estimating methods and terminology contained in this document may not 

conform to the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W 

methods or those in other EPA regulations. 

2011 2