Subsea produced water treatment : challenges and solutions ... · PDF file1 TUV/NEL Produced...

1TUV/NEL Produced Water Club 23rd April 2010

Subsea Produced Water Treatment : Challenges and Solutions for

Deepwater

TUV/NEL Produced Water ClubAberdeen, 23rd April 2010

Wayne Evans – VEOLIA WATER


Agenda

• Applications and needs

• Challenges to go further and deeper

• Saipem / Veolia agreement Principles and objectives for subsea development

• Development work on goingFirst separation stage Produced water treatment

• Conclusion


• Subsea liquid / liquid separation and produced water treatment:• Subsea Separation of water • Subsea water reinjection• Export of oil and gas to surface

Need for water treatment depending on quality required for injection

Principles

To FPSO


Typical production profile

020406080

100120140160180200

0 5 10 15 20

Years

Kbp

d

OIL

WATER

LIQUID

• Mature fields• Topsides debottlenecking of water treatment capacity for additional

satellite fields development• Increase recovery

• New fields:• Increase recovery • Reduce cost

Subsea liquid / liquid separation applications

More water produced than oil


Mature field applications

• Troll Pilot – N. Hydro (June 2000)Water re-injection in a disposal wellTotal liquids: 60 000 blpdWater depth: 340 m

• Tordis – Statoil (Sept. 2007)Water & sand re-injection in a disposal wellIncreased recovery factor from 49% to 55%26 million bbl extra oilWater depth: 210 m

• Next to come: Marlim – Petrobras (2011)Water reinjected in injection wellWater depth: 900 m

State of the art

Station size: 17x17x8 m


Challenges to go further and deeper

• Challenges:• Water depth

Manufacturing of heavy wall pressure vesselsWeight of components (for maintenance with light intervention vessels)

• Water quality required when re-injected into the reservoirComplexity / reliability of advanced process and associated operating modesControlSensorsMaintenance requirements

=> Need efficient and reliable process to guarantee water quality

The development of such subsea systems requires the association of :• water treatment expertise • subsea system capability


Partnership

SAIPEM and VEOLIA PARTNERSHIP

Agreement signed in 2009 between Saipem and Veolia to develop subsea water treatment systems, combining:

Saipem experience and expertise in subsea systems, deepwater technologies, system integration, qualification testing, etc.

Veolia experience and expertise in water processing offshore, equipment design, supply and operation with a long track record


Saipem expertise for subsea process

Experience in very large EPCI deepwater projects: Rosa, Kizomba A & B, Akpo, Usan, …

Since the 90’s:Technology developments in several subsea process areas …

… boosting, gas-liquid separation and liquid-liquid separation, with a focus on deepwater applications.

Multipipe gas/liquid separator

Subsea process from a deepwater perspective


Veolia water treatment expertise

• Packaged Plant:Seawater treatmentProduced water treatment

• Topsides water treatment modules:

Golfinho II modules delivered to Saipem


Saipem / Veolia subsea development

• Objectives:• Development of flexible solutions to subsea water processing to free

operators of the restrictions inherent in current subsea technologies

• Offer solutions to suit the water treatment requirements instead of specifying water quality to meet the capability of the available equipment

• Process • Start from general cases to screen solutions, identify development

needs and propose solutions compliant with deepwater requirements


Investigated solutions and technologies

First separation stageGravity separator/ 3C cyclone

Water treatment

Stage 1Hydrocyclone

Water treatment

Stage 2Flotation

Water treatmentCeramic membranes

To injection wells To injection wells

Inlet

Oil in water

1000 to 2000 ppm

Oil in water 100 ppm

Oil in water 20 ppm

Solid in water 15 ppm

Typical performances


First stage – Separation

• Key drivers: • Produced water treatment: required for high water quality => more sophisticated

process• First separation stage should provide water treatment with required water quality

=> Need for robust and flexible first separation stage

• With high performance first separation stage water treatment stage will be more efficient and reliable

• Investigated technologies:• Gravity separation

Conventional process solution for liquid/liquid separationRobust and reliable

• Cyclonic separationInnovative solutionCompact Efficient


First separation stage Horizontal Gravity Separator

• Designed for ~ 90 kbpd• 1500 m wd

• 3 min residence time• 8 m3 Slug Capacity

• ID: 2.5 m• Ltt: 12.8 m• Wall thick.: 90 mm

• 120 tons empty in air• ~ 0 empty in water • 110 tons in operation

subsea• Additional internal could be used if required • Sand jetting system required• Level sensors for water and oil interfaces monitoring

Robust design but space and weight consuming


First separation stage3C cyclone development

• On going development by Saipem for liquid/liquid separation:3C cyclone (patented)

• Developed to be compatible with subsea application:

Specific cyclone design (plate) coupled with Pressure Regulating Vessel (PRV)

FlexibleLimited control Compact Efficient

• Keys for qualification:• Separation efficiency• Control principle

• Development work:• CFD simulation for design optimization• Control simulation• First qualification tests (2 phases)

90 mm

300 mm


First separation stage3C cyclone - Principle

3C Cyclones PRV

Gas/liquid separation

Water treatment

Light outflow (oil)

Heavy outflow (water)

Gas

To injection well

Preliminary separation

Liquid/liquid separation

Produced water treatment

To surface

Inlet

Subsea separation station

Oil

Liquid

Saipem


First separation stage3C cyclone – Qualification

• Qualification tests• Prototype : Cyclone and PRV

PlexiglasScale 1 cyclone

• Test loop:Instrumentation:

– P & T sensors – Flowmeters– Malvern (oil droplets measurement)– Camera for macro pictures

3 sampling points for separation performance survey

Fluids:– 2 synthetic oils (2 viscosities)– water


First separation stage3C cyclone

• Efficient separation performance • 17 µm cut off at turndown conditions

• Simplified control:• Flexible regarding

Inlet flowrateInlet water cut

• Single valve required at 3C water outlet, infrequently actuated

• Way forward:• Definition of preliminary gas/liquid separation stage • Optimization of PRV arrangement • Definition of next qualification phase (real crude?)


Investigated solutions and technologies

First separation stageGravity separator/ 3C cyclone

Water treatment

Stage 1Hydrocyclone

Water treatment

Stage 2Flotation

Water treatmentCeramic membranes

To injection wells To injection wells

Inlet

Oil in water

1000 to 2000 ppm

Oil in water 100 ppm

Oil in water 20 ppm

Solid in water 15 ppm

Typical performances


Produced water treatment

Water processing options• First the sand must be removed:

• Desanding hydrocyclones

• Then oil removal is required:• Deoiling hydrocyclones for bulk oil removal• Flotation for residual oil removal

• Or we remove the oil and residual solids together:• Ceramic membranes


Produced water treatment - Desanding

Desanding Hydrocyclones• Sand separation and handling critical to any

subsea water treatment system• High pressure wellhead systems already

operational – no difficulty in marinization

• Subsea challenges:TurndownSand settlingSeparator jetting

• Solutions:Eductor technology already availableSolids returned to export line to avoid localised discharge


Produced water treatmentDeoiling Hydrocyclone

Status• Hydrocyclone technology is well

understood with high reliability for subsea operations

• Challenges:Hydrocyclones do not respond well to turndownContinuous adjustment of reject impossible without control valve

• Solutions:Pressure balanced system maintains best practicable operationReduced efficiency counteracted by flotation unit downstream


Subsea Flotation Unit

Status• Based on CoPhaseTM CFU.• Self-adjusting flotation unit with no

external power or gas requirement and no recirculation pumps

• Challenges:Eductors to be redesigned for high pressure operation followed by high pressure testingLevel/pressure control valves unavailable

• Solutions:Pressure balanced system maintains best practicable operation


Produced water treatmentMembranes

• Reinjection below fracture pressure requires removal of emulsified oil (<20 micron droplets) and fine solids (<1 micron particles)

• In order to go below 20 microns oil and solids treatment, we need something different:

• Ceramem® ceramic membranes being adopted topsides:

Will separate highly emulsified oilsRemove all solids > 0.1 micronTolerant of high inlet solidsSuitable for high temperature operationEasily cleaned

• However: topsides performance still not predictable


Ceramic membranes

• Challenges:• Improve predictability of membrane fouling

performance. (Characterisation programme underway)

• Hyperbaric membrane testing required (no problems envisaged)

• Backflushing and cleaning solutions needed (conceptual design complete)

• Chemical storage solutions required (conceptual design well advanced)

• Subsea controls for batch cleaning operations (solutions available)

• Online monitoring of very low quantities of solids and oil

CIP

MembranesFeed

Concentrate

Permeate


Subsea station integration

• Integration of all equipment in subsea station:• Challenge for subsea control and monitoring

Analysis of both standard electro-hydraulic and all electric systems (electric actuated valves)Need for subsea sensors development to monitor oil in water content

• Challenge for maintenanceReplacement of modules Definition of reliability andintervention requirements(Capex vs. Opex)


Development is on- going for water treatment process meeting the followingrequirements for reinjection into the reservoir:

• 20 ppm of oil in water • 15 mg/l of solids in water

• Next steps:

Conclusion

2010 2011 2012 20142013 2015

First full scale installation

Define design cases, complete conceptual design

and cost estimates

High pressure testing and marinized design

Subsea pilot trial

We are at the beginning of this development to be done in cooperation with oil companies.

Operators are welcome to advise on design cases

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