Lessons Learned from the 

Natural Gas STAR Program 

Installing Vapor Recovery Units 

Source Reduction Training 

Interstate Oil and Gas 

Compact Commission 

Charleston, West Virginia 

February 27, 2009 

epa.gov/gasstar 

Reduction Opportunities: Agenda 

Methane Losses
 

Methane Savings
 

Is Recovery Profitable?
 

Industry Experience
 

Lessons Learned
 

1 

1
Methane Losses from Storage Tanks 

U.S. natural gas production sector emissions in 2006 

Well Venting Storage Tank Other 

Meters and
 

Pipeline Leaks
 

8 Bcf
 

Compressor Fugitives, 

Venting, and Engine
 

Exhaust
 

13 Bcf
 

and Pumps Operations 13 Bcf 

29 Bcf 

EPA. Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990 – 2006. April, 2008. Available on the web at: 

epa.gov/climatechange/emissions/usinventoryreport.html 2 Natural Gas STAR reductions from gathering and boosting operations have been moved to the production sector. 

Sources of Methane Losses 

A storage tank battery can vent 5,000 to 500,000 thousand

cubic feet (Mcf) of natural gas and light hydrocarbon vapors to 

the atmosphere each year 

Flash losses 

Occur when crude oil or condensate is transferred from a gas-oil 

separator at higher pressure to a storage tank at atmospheric pressure 

Working losses 

Occur when crude or condensate levels change and when liquid in

tank is agitated 

Standing losses 

Occur with daily and seasonal temperature and barometric pressure

changes 

3 

2

Venting 

6 Bcf 

Sources 

8 Bcf

and Flaring 

8 Bcf 

Pneumatic 

Devices 

48 Bcf 

Dehydrators Offshore 
Tank Venting Emissions 

Video recording of tank venting emissions 

Video provided by Hy-Bon Engineering 

4 

Methane Savings: Vapor Recovery 

Vapor recovery can capture up to 95% of

hydrocarbon vapors from tanks
 

Recovered vapors have higher heat content than

pipeline quality natural gas 

Recovered vapors are more valuable than natural

gas and have multiple uses 

5 

3
Types of Vapor Recovery Units 

Conventional vapor recovery units (VRUs) 

Venturi ejector vapor 

recovery units

(EVRUTM) or Vapor

Jet
 

Use Venturi jet 

ejectors in place of 

rotary compressors
 

6 

7 

Conventional Vapor Recovery Unit 

Crude Oil 

Stock 

Tank(s) 

Control 

Pilot 

Vent Line 

Back Pressure Valve 

Suction 

Scrubber 

Suction 

Line 

Condensate 

Return 

Bypass 

Valve 

Electric 

Control 

Panel 

Electric Driven 

Rotary Compressor 

Gas Sales 

Meter Run 

Gas 

Liquid 

Transfer Pump 

Check Valve 

Source: Evans & Nelson (1968) 

Sales 

4
8 

Vapor Recovery Installations 

9 

Venturi Jet Ejector* 

High-Pressure 

Motive Gas 

(~850 psig) 

Flow Safety Valve 

Pressure Indicator Temperature Indicator 

PI TI

TI

PI

Low-Pressure Vent Gas from Tanks 

(0.10 to 0.30 psig) 

PI TI

Discharge Gas 

(~40 psia) 

Suction Pressure 

(-0.05 to 0 psig) 

*EVRUTM Patented by COMM Engineering 

Adapted from SRI/USEPA-GHG-VR-19 

psig = pound per square inch, gauge 

psia = pounds per square inch, absolute 

5
 

10 

Vapor Recovery with Ejector 

Oil to Sales 

Gas to Sales 

@ 1000 psig 

LP 

Separator 

Oil 

Gas 

Compressor 

Ejector 

Oil & Gas 

Well 

5,000 Mcf/day Gas 

5,000 barrels/day Oil 900 Mcf/day 

Ratio Motive / Vent = 3 

= 900/300 

300 Mcf/day Gas 

40 psig 

6,200 Mcf/day 

Crude Oil Stock 

Tank 

(19 Mcf/day incremental 

fuel) 

281 Mcf/day 

Net Recovery 

Mcf = Thousand cubic feet 

11 

Vapor Jet System* 

*Patented by Hy-Bon Engineering 

6
 

12 

Vapor Jet System* 

*Patented by Hy-Bon Engineering 

• Utilizes produced water in closed loop system to effect gas gathering from tanks 

• Small centrifugal pump forces water into Venturi jet, creating vacuum effect 

• Limited to gas volumes of 77 Mcf/day and discharge pressure of 40 psig 

Criteria for Vapor Recovery Unit

Locations 

Steady source and sufficient quantity of losses 

Outlet for recovered 

gas 

Tank batteries not 

subject to air

regulations 

13 

7
Quantify Volume of Losses 

Estimate losses from chart based on oil 

characteristics, pressure, and temperature at each

location (± 50%) 

Estimate emissions using the E&P Tank Model 

(± 20%)
 

Engineering Equations – Vasquez Beggs (± 20%) 

Measure losses using recording manometer and well

tester or ultrasonic meter over several cycles (± 5%) 

14
 

Estimated Volume of Tank Vapors
 Vapor Vented from Tanks, cubic foot / barrel Gas/Oil Ratio 

110 

100 

90 

80 

70 

60 

50 

40 

30 

10 

20 

Under 30° API

30° API to 39° API

40° API and Over 

API Gravities 

10
 20 30 40 50 60 70 80
 

Pressure of Vessel Dumping to Tank (Psig) 

o API = API gravity 15
 

8
Estimated Volume of Tank Vapors 

Atmospheric tanks may emit large amounts of tank

vapors at relatively low separator pressure 

bbl – barrels 16 

Vasquez-Beggs Equation 

psig – pounds per square inch, gauge 

scf – standard cubic feet 

What is the Recovered Gas Worth? 

Value depends on heat content of gas 

Value depends on how gas is used 

On-site fuel 

Natural gas pipeline 

Gas processing plant 

Gross revenue per year = (Q x P x 365) + NGL 

Q = Rate of vapor recovery (Mcf per day) 

P = Price of natural gas 

NGL = Value of natural gas liquids 

17 

9
=

Value of Natural Gas Liquids
 1 2 3 4 

Btu/gallon MMBtu/ $/gallon $/MMBtu1,2 

gallon (=3/2) 

Methane 59,755 0.06 0.42 7.00 

Ethane 74,010 0.07 0.37 5.21 

Propane 91,740 0.09 0.68 7.58 

n Butane 103,787 0.10 0.86 8.60 

iso Butane 100,176 0.10 0.91 9.08 

Pentanes+* 105,000 0.11 1.01 9.14 

5 6 7 8 9 10 11 

Btu/cf MMBtu/Mcf $/Mcf $/MMBtu Vapor Mixture Value 

(=4*6) Composition (MMBtu/Mcf) ($/Mcf)

( 8*10) 

Methane 1,012 1.01 $7.07 7.00 82% 0.83 $5.81 

Ethane 1,773 1.77 $9.23 5.21 8% 0.14 $0.73 

Propane 2,524 2.52 $19.10 7.58 4% 0.10 $0.76 

n Butane 3,271 3.27 $28.11 8.60 3% 0.10 $0.86 

iso Butane 3,261 3.26 $29.58 9.08 1% 0.03 $0.27 

Pentanes+ 4,380 4.38 $40.02 9.14 2% 0.09 $0.82 

Total 1.289 $9.25 

1 – Natural Gas Price assumed at $7.00/MMBtu 

2 – Prices of Individual NGL components are from Platts Oilgram for Mont Belvieu, TX February 17, 2009 

18 

Cost of a Conventional VRU
 

Vapor Recovery Unit Sizes and Costs 

Capacity

(Mcf/day) 

Compressor 

Horsepower 

Capital Costs 

($) 

Installation Costs 

($) 

O&M Costs 

($/year) 

25 5 to 10 20,421 10,207 to 20,421 7,367 

50 10 to 15 26,327 13,164 to 26,327 8,419 

100 15 to 25 31,728 15,864 to 31,728 10,103 

200 30 to 50 42,529 21,264 to 42,529 11,787 

500 60 to 80 59,405 29,703 to 59,405 16,839 

Cost information provided by United States Natural Gas STAR companies and VRU manufacturers, 2006 basis. 

19 

10
Is Recovery Profitable?
 

Financial Analysis for a Conventional VRU Project 

Peak 

Capacity

(Mcf/day) 

Installation 

& Capital

Costs1 

($) 

O&M 

Costs 

($/year) 

Value of 

Gas2 

($/year) 

Annual 

Savings 

($) 

Simple 

Payback 

(months) 

Internal 

Rate of 

Return 

25 $35,738 $7,367 $77,106 $69,739 10 121% 

50 $46,073 $8,419 $154,213 $145,794 6 204% 

100 $55,524 $10,103 $308,425 $298,322 4 352% 

200 $74,425 $11,787 $616,850 $605,063 3 537% 

500 $103,959 $16,839 $1,542,125 $1,525,286 2 974% 

1 – Unit cost plus estimated installation of 75% of unit cost 

2 – $16.90 x 1⁄2 peak capacity x 365, Assumed price includes Btu enriched gas (1.289 MMBtu/Mcf) 

20 

Industry Experience: EnCana Oil & Gas 

Vapor recovery unit installed in Frenchie Draw, WY 

Captures vapors from 

Separators 

Crude oil storage tank 

Non-condensable dehydrator still gas 

VRU designed to handle 500 Mcf/day 

Additional capacity over the estimated 284 Mcf/day of total 

gas from all emission sources 

21 

11
22 

Industry Experience: EnCana Oil & Gas 

Quantify the volume of vapor emissions 

352'<&7,21 <1,7

75($7(5

OIL 

,1/(7 6(3$5$725

OIL 

200 PSIG 

125 PSIG 

40 PSIG 

7$1. '(+ @'5$7,21 <1,7

=5<

OIL 

1 

2 

3 

4 5 

ATM ATM 

GAS 

GAS GAS 

ATM SUCTION 

125 PSIG DISCHARGE 

1 FLASH LOSS (125 PSIG - ATM PSIG) 

2 FLASH LOSS (200 PSIG - ATM PSIG) 

3 FLASH LOSS (40 PSIG – ATM) 

4 WORKING & BREATHING LOSS 

5 STILL VENT NON CONDENSIBLE 

(AT WELL LOCATION) 

GAS 

Total Emissions284 MSCFD 

Source: EnCana Oil & Gas (USA) Inc. 

EnCana Oil & Gas: Project Costs 

Determine the cost of VRU project 

Installation 

VRU Unit (500 Mcfd) - $90,000 

Generator- $85,000 

Vent Header- $25,000 

Labor- $200,000 

TOTAL $400,000 

O & M 

VRU Unit (500 Mcfd) - $15,000 

Generator- $18,000 

Fuel- $73,000 

TOTAL $106,000 23 

12
EnCana Oil & Gas: Project Economics 

Evaluate VRU economics 

Capacity– 500 Mcfd 

Installation Cost ­ $400,000 

O&M­ $106,000/year 

Value of Gas*­ $788,400/year 

Payback­ 7 months 

Return on Investment­ 170% 

*Gas price assumed to be $ 7.60 by Encana 

24 

Industry Experience: Anadarko 

Vapor Recover Tower (VRT) 

Add separation vessel between heater treater or low 

pressure separator and storage tanks that operates at 

or near atmospheric pressure 

Operating pressure range: 1 psi to 5 psi 

Compressor (VRU) is used to capture gas from VRT 

Oil/Condensate gravity flows from VRT to storage tanks 

25 

13
 

 

 

 

 

 

 

 

Industry Experience: Anadarko 

VRT reduces pressure drop from approximately 50

psig to 1-5 psig
 

Reduces flashing losses
 

Captures more product

for sales
 

Anadarko netted between 

$7 to $8 million from 1993 

to 1999 by utilizing 

VRT/VRU configuration
 

Courtesy of Anadarko 

26 

Industry Experience: Anadarko 

Standard size VRTs available based on oil 

production rate 

20” x 35’ 

48” x 35’ 

Anadarko has installed 

over 300 VRT/VRUs

since 1993 and 

continues 

on an as needed basis 

Equipment Capital 

Courtesy of Anadarko Cost: $11,000 

27 

14
Lessons Learned 

Vapor recovery can yield generous returns when there are 

market outlets for recovered gas 

Potential for reduced compliance costs can be considered 

when evaluating economics of VRU, EVRUTM, or Vapor Jet 

VRU should be sized for maximum volume expected from

storage tanks (rule-of-thumb is to double daily average

volume) 

Rotary vane, screw or scroll type compressors recommended 

for VRUs where Venturi ejector jet designs are not applicable 

EVRUTM recommended where there is a high pressure gas

compressor with excess capacity 

Vapor Jet recommended where there is produced water, less 

than 75 Mcf per day gas and discharge pressures below 40 

psig 

28 

Discussion 

Industry experience applying these technologies and

practices 

Limitations on application of these technologies an

practices 

Actual costs and benefits 

29 

15