## 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

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# 1

# Methane Losses from Storage Tanks U.S. natural gas production sector emissions in 2006

Storage Tank Well Venting 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

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# 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

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# 3

# Types of Vapor Recovery Units Conventional vapor recovery units (VRUs) Venturi ejector vapor recovery units (EVRU TM 

# ) 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



# 48 

# 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)

*EVRU TM Patented by COMM Engineering Adapted from SRI/USEPA-GHG-VR-19 psig = pound per square inch, gauge psia = pounds per square inch, absolute



# 510 

# 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



# 612 

# Vapor Jet System*

*Patented by Hy-Bon Engineering 

### • Utilizes produced water in closed loop syst em 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

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# 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%)

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# Estimated Volume of Tank VaporsVapor Vented from Tanks,cubic foot / barrelGas/Oil Ratio 110 100 90 80 70 60 50 40 30

10 20 U nde r 3

0

° A P

I 3

0

° A PI to 3 9

° A PI 4

0 ° A

PI a n d O v e

rAPI 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

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# 9= 

# Value of Natural Gas Liquids

1 2 3 4 Btu/gallon MMBtu/ $/gallon $/MMBtu 1,2 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 Pla tts 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.

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# 10

# Is Recovery Profitable?

Financial Analysis for a Conventional VRU Project Peak Capacity (Mcf/day) Installation & Capital

Costs 1



### ($) O&M Costs ($/year) Value of Gas 2 

### ($/year) Annual Savings ($) 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)

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# 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

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# 1122 

# Industry Experience: EnCana Oil & Gas Quantify the volume of vapor emissions

3 52'<&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 betwe en heater treater or low pressure separator and stor age 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 grav ity flows from VRT to storage tanks

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# 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

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# 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

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# 14

# Lessons Learned Vapor recovery can yield gener ous returns when there are market outlets for recovered gas Potential for reduced complianc e costs can be considered when evaluating economics of VRU, EVRU TM 

# , 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 scro ll type compressors recommended for VRUs where Venturi ejector jet designs are not applicable EVRU TM 

# 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

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# 15