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Exploration & Production Technologydelivering breakthrough solutions
Afternoon Wrap-Up: An Overview ofProduced Water Treatment Technologies
James C. Robinson, P.E.,Sr. Water Technology Engineer, EPTG
Nov. 8, 2007
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Recent Water Technology in the News
From industry byproduct to usable resource: Company unveils water purification system fornatural gas wells
www.daily-times.com/ci_6588245
Texas A&M to host demonstration of produced water purification unit www.mywesttexas.com/site/news.cfm?newsid=18641031
Technology may hold refinery solution
www.indystar.com/apps/pbcs.dll/article?AID=/20070809/LOCAL/708090528
Water, nanotechnology's promises, and economic reality
www.nanowerk.com/spotlight/spotid=2372.php
Innovative technologies are applied to phase out shallow-water disposal in Oman
www.eandpnet.com/area/prod/530.htm
TX commission approves projects to recycle water at Barnett shale gas drilling sites
www.rrc.state.tx.us/news-releases/2006/103106.html
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The Plan
Basis of Design
Treatment Technologies
Resources for Additional Information
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Operations and Technologies Offshore
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Produced Water Treatment Objectives
De-oiling primarily for discharge to the environment
De-sanding primarily for Re-Injection (PWRI)
Pollutant reduction/removal soluble pollutants, metals, etc.
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Produced Water Treatment Basis of Design
Influent water quality characterization
Produced Water characteristics: WSOs, Solids, Temperature
Produced Oil properties (API gravity, Oil-in-water droplet size distribution)
Temporal Variability / Dynamic (hourly & over life of facility)
Produced water flowrate
Oil-in-water concentration Solids concentration and particle size in produced water
Effluent water quality treatment specifications
Overboard discharge
Environmental Protection
Discharge Limitations (Oil-in-Water, Toxicity, etc.)
Produced Water Re-Injection (PWRI)
Equipment Operability (pumps, flowlines, screens) Sustainable Injectivity (formation plugging)
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Technology Selection Additional Considerations
Water Injection Necessity / Benefits (Enabled / Improved Production)
Produced Water Re-Injection (PWRI)
Seawater Injection
Production chemicals, Well Treatment, Flow Assurance (Impacts)
Weight / Footprint
Motion (Floating Facilities) Reliability / Redundancy
Operability / Simplicity / Maintenance Intensity
Scale & Corrosion Management (inhibition)
Amenable to future modification / modular design
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Production Chemical Impacts
Production chemicals are required to protectthe production system and achieve targetoil and water specifications
Hydrate Inhibitor
Corrosion Inhibitor
Demulsifier
Water clarifiers
Most production chemicals aresurface active agents
Overdosing or incompatible chemicalscan create problems
Corrosion Inhibitors might impact separationand water quality
Excess demulsifier can create emulsions
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Technology Identification
Starting Point:Water Quality
Flow / Variability
Field LifeChemicals
End Point:
Treatment Specifications
(Re-Use / Disposal)Environmental Protection
Treatment Technologies:
Reliability / Redundancy
Size / Weight
HydrocyclonesIGF/MBF/DGF/CFU
CoalescersAbsorption
Media FiltrationMembrane Filtration
ExtractionOxidation
EvaporationRe-InjectionChemicals
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The Plan
Basis of Design
Treatment Technologies
Resources for Additional Information
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Established / Recent / Emerging Technologies
De-Sanding / Solids Filtration
Gravity separation
De-Sanding (Solid/Liquid) Hydrocyclones
Media filtration (sand filter / dual media filter / deep bed filter)
Physical barrier (cartridge / sock)
Membrane Separation (MF)
De-Oiling
Gravity separation
Coalescence enhanced gravity separation
De-Oiling (Liquid/Liquid) Hydrocyclones
Gas Flotation
Absorption (organoclay, etc.)
Walnut Shell Media Filtration
Membrane Separation (ceramic, vibrating)
EstablishedRecentEmerging
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Established / Recent / Emerging Technologies
Polishing - soluble pollutant removal
Absorption (Activated Carbon, Organoclay, etc.)
Aeration & sedimentation (for iron removal)
Partitioning Manipulation (enticing soluble pollutants into oil phase prior to De-Oiling)
Solvent Extraction
Biological treatment (membrane bio-reactor, fixed film, etc.)
Oxidation Membrane Separation (UF & NF)
Polishing - salinity reduction
Membrane Separation (RO)
Ion Exchange Electrodialysis (ED)
Evaporation (Freeze/Thaw, ponds, etc.)
Thermal distillation
Polishing - salinity reduction & soluble pollutant removal Membrane Separation (RO)
Constructed Wetlands
EstablishedRecentEmerging
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Ga
sFoam
Free Settling
Hindered Settling
Dense Packed
Water
Sand
Section Through Separator
Typical 3-Phase Separation
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Primary Oil / Water Separation Technologies
SEPARATOR TYPE TECHNOLOGYOI L DROPLET
SI ZE REMOVAL
API Separator Gravity >150 mCPI / TP
SeparatorGravity w/Coalescer >50 m
DGF / I GF
Gas Flotat ion Gas Flotation >20 m
De-OilingHydrocyclones
Centrifugal Force >10 m
CoalescingMedia Filt rat ion
Adsorption >2 m
AbsorptionMedia Filt rat ion
Absorption
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0 10 20 30 40 50
Typical Minimum Effluent Oil-in-Water Concentration Achieved (ppm)
Absorbent Media Filtration
Gas Flotation
De-Oiling Hydrocyclones
Membrane Filtration
Cos
t
De-Oiling Technology Cost & Capability
Generally
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Gas Flotation
Injected gas bubbles attach to oil droplets, reducing their density
Most effective when gas bubbles size < oil droplet size
Oil is then skimmed off as a froth (a.k.a. float)
Gas is introduced
IGF mechanically via paddles or via eductor
DGF - dissolving under pressure and then releasing
Typically delivers 25 ppm oil-in-water concentration
from inlet containing oil droplets larger than 20 m
More effective with chemical addition (coagulants + flocculants)
Can remove up to 70% suspended solids
Disadvantages
Sensitive to platform motion (due to surface skimming)
Poor response to change in feed concentrations or flow rates
Units are typically large / bulky and heavy
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Gas Flotation - Rise Velocity Comparison
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Gas Flotation Float
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Belt drive
Motor
Shaft
Gas drawn in
Disperser breaks
gas into minutebubbles
Launder
Oil rejectT71
Rotor
Disperser
T71
Disperser hood
Weir
Skimmer paddles
Gas Flotation Equipment Mechanical IGF
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Vertical IGF
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Horizontal, Multi-Chamber, Gas Flotation
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Dissolved Gas Flotation (DGF)
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Compact Flotation Unit (CFU)
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De-Oiling Hydrocyclones
Disadvantages
Min. operating pressure drop (4-5bar)
Flow operating range too much or too little flowcauses drop in efficiency
Solids erosion / carryover
Advantages
Small footprint, compact
Efficient - typical performance 20 mg/l
Motion independent Inlet feed quality - Typically >10 micron
No chemical generally required
Low maintenance
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De-Oiling Hydrocyclones
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De-Oiling Hydrocyclones
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Coalescers
Coalescence is theformation / combinationof smaller dropletsinto larger droplets
Coalescence takes placeon the fibres of a cartridge,within a resin bedor a structured packing
Disadvantages:
blockage by solids /requires pre-filtration
surface deactivation bysurface active chemicals
Droplet size dependent
Oil Droplets
Captured On
Fibresor resin
AdjacentDroplets
Coalesce
Fibre orresin bed
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Typical Onshore Treatment for Re-Injection
Characteristics
Relatively long retention times for gravity separation are feasible due to practicality ofinstalling larger tanks
Relatively high treatment specification for oil-in-water concentration due to PWRI
Standard Technologies Employed
Gravity Separation (Gun-Barrel Separator)
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Typical Offshore Treatment for Discharge
Characteristics
Relatively short retention times for gravity separation due to necessity for minimalvessel weight and footprint
Relatively low treatment specification for oil-in-water concentration due to
environmental discharge limits Standard Technologies Employed - Pre~1990s:
Skimmer vessel, followed by
Mechanical Induced Gas Flotation
Standard Technologies Employed - Post~1990s: De-oiling Hydrocyclones, followed by
Degasser vessel or Gas Flotation
Supplemental (Tertiary) Technology(if/when necessary)
Absorption filtration(carbon, organoclay, proprietary clay-products)
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Generalities
A single Water Treatment Technology is usually not a complete solution
Often, treatment in stages is necessary
Often, pre-treatment is necessary to protect and enable downstream processes
Real systems have variations in flowrate, water quality Real systems are subject to abuse, neglect and operating errors
Often, treatment processes will concentrate pollutants into a smaller volume of water(often 5% - 35%), which will have highly concentrated pollutants, and will still require
disposal or management. For Example:
1000 bbls volume
800 bbls volume
water treatment
technology
process
& 200 bbls volume
100 ppm pollutants 1 ppm pollutants 496 ppm pollutants
wastewater treated water concentrate
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Key Points Technology Selection
Design the produced water oil-in-water removal system based on:
Water quality in (from wells, separators)
Water quality out (specifications for discharge/PWRI) Oil droplet size distribution
Variability in flowrate / oil concentration / solids / etc.
Production chemicals / WSOs / solids / scale
Future expandability / modifications
Demands: operability / weight / footprint
Take Produced Water Treatment Seriously
Critical to Oil Production
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The Plan
Basis of Design
Treatment Technologies
Resources for Additional Information
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