Vapor Recovery in Offshore
Applications
Gulf Coast Regulatory and
Environmental Affairs Group Meeting
July 11, 2013
Air Quality Regulations
►
BOEM/BSEE has jurisdiction for Western/Central
Gulf of Mexico air quality for oil and gas drilling and
production operations.
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East of 87.5 degrees longitude jurisdiction of OCS
waters is USEPA Region 4.
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States have jurisdiction for air quality for onshore
and coastal/territorial seas.
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Texas territorial waters (and county line) extend for
three marine leagues (10.36 statute miles) offshore
Texas
VRU Drivers – Onshore/Coastal Areas
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May need vapor recovery to meet state permitting rules
or federal standard that apply to onshore, coastal and
territorial seas.
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Limits flash gas to meet permit limits in general permits
(Louisiana) or permit-by-rule (PBR) permits (Texas)
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Normally an option for permits, not always mandated.
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Option used to meet control requirements for storage
tanks in 40 CFR 60 Subpart OOOO New Source
Performance Standard - Oil and Natural Gas Sector
VRU Drivers – Western/Central GOM
30 CFR 250.1160 When may I flare or vent gas?
►(a)(5)
You may not flare or vent more than an average
of 50 MCF per day during any calendar month without
Regional Supervisor approval. Limit of 50,000 SCFD
average flash gas vent/flare gas limit (30 CFR
250.1160).
►Recover
flash gas if economical to recover gas
VRU Drivers – Western/Central GOM
30 CFR 250.1160 When may I flare or vent gas?
►
(b) states that must not flare or vent gas over the
volume approved in your Development Operations
Coordination Document (DOCD) or in Development
and Production Plan (DPP) submitted to BOEM.
►
Typically this volume is in the “Air Quality Review
(AQR)” spreadsheets submitted with DOCD
Typical Production Process
Tank Vent Gas Quantification
►
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Must be something generally accepted by industry
and regulators.
Options include:
1. Direct measurement of tank vent
2. Collect/analyze pressurized oil and measure gas to
oil ratio (GOR)
3. Pressurized oil sample/analyses as input to
Equations of State computer simulation or API E&P
Tank computer pgm.
Data collection (Direct Measurement)
IQR Process –
Measurement Protocol
►
Simple & easy way to
measure volume of vent
gas with 98% accuracy
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Flow characteristics
identified
(very cyclical)
►
Gas composition
analyzed
Why Vapor Recovery?
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Regulatory compliance
Recover very rich flash gas - $$
Reduce emissions of VOCs and greenhouse
gases
Improve safety of facilities
Engineered Solution Design
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Volume & peaks of flow
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Composition(s) of gas. H2S?
►
Pressures
►
Temperatures
►
Availability of utilities (power/motive gas)
►
Availability of booster compression
►
Markets for products
Types of Solution Package Technologies
Traditional vapor recovery uses compressors
driven by electric or natural gas engines
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Reciprocating compressors
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Rotary screw compressors
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Rotary vane compressors
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Scroll compressors
Ejector Vapor Recovery Unit (EVRU™)
Reciprocating Compressors
►
High pressure &
volumes
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Automatic bypass
(recycle)
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Not recommended for
wet gas
Flooded Screw Compressors
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High pressure differentials
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High volume capacities
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Variable Frequency Drive
(VFD)
►
Oil dilution issues
Rotary Vane Compressors
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High volume capacities
►
VFD or bypass
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No oil dilution
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Low pressure differentials
60 psig in single stage
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Vane wear
Scroll Compression
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Less moving parts
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Less maintenance
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VFD
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Oil dilution issues
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20 ppm H2S limit
Application of Scroll Technology
►Recovering
gas from oil storage tanks and heater
treater and discharging pressurized gas to larger
compressor
►VRU
system requires electrical power and purge
gas for recycle
►High
molecular weight gas recovery
Scroll Compressor Case Example
Dual CVRU package for Offshore Application
Design criteria
• Recovered gas throughput: 150,000 SCFD (150 MSCFD)
• Vent gas source: atmospheric storage tanks
• Suction Pressure: 1 to 3 inches water column
• Discharge Pressure: 100 psig
• Discharge to suction of onsite larger compressor
Offshore Scroll System
SPE-127153-PP Paper Conclusions
►
Recovers natural gas product
►
Lowers emissions of VOCs and GHGs
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Lower maintenance costs than typical VRUs
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System requires smaller footprint
►
Cost effective and efficient VRU for offshore
environment
COMM Patented EVRU™
Motive
$$$$$$$$$
Suction
Discharge
EVRU™ Case Study Economics
►
Investment: $120,000
►
700 BOPD of 62 API Gravity
►
Average gas recovery: 175 MCFD
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$709,560/year product recovery at $6/MMBTU
►
Payback period: 2 months
EVRU™
Eagle Ford Onshore
Offshore Africa
Offshore GOM EVRU™
EVRU System Advantages
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Simple, non-mechanical vapor recovery system
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100% run time and on/off provides turndown
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Handles rich, wet gas & H2S
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No oil to maintain
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Small footprint
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Easy to modify
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Texas allows emission control efficiency of 99%
Key Points for a VRU Solution
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Determine regulatory requirements
Value of natural gas recovered
Cost of VRU capital costs and operation costs
Knowing facility process and gas to be recovered
critical to design and effective operation of VRU
Measure & sample gas if possible
Consider redundancy or easy replacement
options
1319 West Pinhook Road
Lafayette, Louisiana USA
Brian Boyer
Salah Mansour
(337) 237-4373
www.commengineering.com