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ELECTROSTATIC DESTABILIZATION OFWATER-IN-OIL EMULSIONS:

USE OF LABORATORY SCALE EXPERIMENTS TO DEBOTTLENECK AND OPTIMIZE SEPARATION PROCESSES

21 November 20121 Wrtsil

ERIK BJRKLUNDTOULOUSE WORKSHOP 2012

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OUTLINE

Separation and electrostatic destabilization Basic mechanisms

Controlling the outcome Modelling and experiments Model oil versus real crudes

Use of electrostatic destabilization as a debottlenecking tool

21 November 2012 Presentation name / Author, Document ID:2 Wrtsil

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SEPARATION AND ELECTROSTATIC DESTABILIZATION

21 November 20123 Wrtsil

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Separation process can be divided into a sedimentation process and a coalescence process: Sedimentation of water droplets in oil can be modeled by using the terminal

velocity of water droplets:

The sedimentation is proportional to the droplet diameter squared.

The larger the droplet, the faster it separates from the oil.

Coalescence of droplets is governed by a balance between attractive forces due to gravity and repulsive forces due to presence of surfactants.

SEPARATION PROCESS

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=

=

1

10

100

1000

10000

0 100 200 300 400 500 600

Tim

e (m

in)

Drop size (micron)

Settling time in the oil layer Example of sedimentation:

Mono-dispersion. Density:

Water: 1000 kg/m3

Oil: 878 kg/m3

Viscosity: 5.4 cP. Oil height: 1.0 m.

BrukernavnPresentasjonsnotaterHer m jeg vise at dette tar tid og at det ofte er en flaskehals. Hva kan vi jobbe med? Vi kan gjre d strre.

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ELECTRO-COALESCENCE

An electric field over an water-in-oil emulsion will set up attractive forces between the water droplets. The attractive forces appear because of the large difference in electrical

properties of oil and water. The water molecules aligns with the field, making the droplets polarized. Oil must be the continuous phase.

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The attractive electrical forces are balanced by drag forces on the droplets.

The coalescence time is given by:

Example: WC: 45 %

Viscosity: 5.4 cP

Tel: 0.65 ms

ELECTRO-COALESENCE

+

=

11158 50

12

0 dsdETel

e

el

t

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BATCH TEST EXAMPLE

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CONTROLLING THE OUTCOME

21 November 20128 Wrtsil

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TRANSPORT EQUATION

Navier-Stokes equation including electrical forces:

Maxwell stress tensor:

Introducing characteristic scales:

Dimensionless groups:

Assumptions: Repulsive forces due to surface active components are negligible compared to

electrostatic induced forces Mild turbulence; large eddies created predominately by separation of fluids

21 November 20129 Wrtsil

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WRTSILS FLOW LOOP RIG

Required total volume = 80l

Schematic for the flow loop rigs (Laboratory Multiphase Platform)

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LABORATORY MULTIPHASE PLATFORM

Plexiglass flow loop rig: Crude oil studies < 50 C HT flow loop rig: Crude oil studies < 100 C, < 22.3 API

Large scale rig: Model oil studies and hardware tests Demo loop rig: Demonstrations and marketing

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Establishing a separation model: Classify separation efficiency according to the relevant parameter groups,

and verify that the separation efficiency remains invariant with respect to these.

Formulate a theory that describes how the separation efficiency varies as a function of the identified parameter groups.

Following this approach, Wrtsil has established a scale-invariant separation model that gives a fit to all flow loop separation results.

The separation model depends on two dimensionless groups and :

SEPARATION MODELING

= (,)

: residual water in oil=(d0,em,,tE,E): effect of electric field on coalescence rate=(d0,em,,,H,tS): effect of gravity

BrukernavnPresentasjonsnotaterThe parameters encode the effect of time in field, electric field strength, emulsion water cut, settling time, viscosity, settling height etc.

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SEPARATION MODEL

Initial water cut = 30% Viscosity = 30cP Density difference =

90kg/m3

Oil layer height = 1.3m Electric field strength =

2kV/cm Initial droplet median

droplet size = 30m

BrukernavnPresentasjonsnotaterTwice as high viscosity about twice as much time in the electrical field to achieve the same effect.

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MODEL OIL VERSUS REAL CRUDE

The attractive electrostatic forces are dominant compared to the repulsive forces caused by surfactants, except if the surfactants are particles: Given the correct demulsifier, a crude oil will behave as a model oil when

utilizing electric fields for destabilization. Experience also shows that the amount of demulsifier can be significantly

reduced.

21 November 2012 Presentation name / Author, Document ID:14 Wrtsil

Typically a significantly reduction in desmulsifier dosage can be achieved when electro-coalescence is applied.

0

5

10

15

20

25

30

35

0 1 2 3 4 5

Wat

er in

Oil

(%)

Time (min)

VIEC ON

VIEC OFF

Demulsifier A

Demulsifier B

Demulsifier B0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00

BS&

W [%

]

Settling time [min]

Comparison real crude vs Model Oil

Real crude, Demulsifier A, VIEC ON

Model oil, VIEC ON

Appropriate demulsifier gives the same behavior for the real crude as a model oil with the same bulk properties.

Incorrect demulsifier can deteriorate the separation enhancement of utilizing electro-coalescence.

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SCALING FROM LABORATORY TO FULL SCALE VERIFICATION

Statoil test loop

35C

40C

50C60C

70C

API 19 crude oil from a North Sea field

Tests carried out at five different temperatures

Temperature [C]

Viscosity@op. pres. [cP]

35 80

40 62

50 38

60 26

70 17

VIEC and VIEC-LW elements at Statoils test loop in Porsgrunn, Norway

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API 40 INSTALLATION COMPARISON WITH MODEL

The VIEC system was installed and commissioned by Wrtsil in January 2012 Performance tests were carried out by a third-party laboratory hired by client to

verify and confirm the enhanced performance due to the VIEC system. The testing was carried out continuously over a two week period.

The following results were reported by the third-party laboratory: A BS&W of less than 0.2% was measured during the whole test period (target was less

than 2%). The salt content in the crude was reduced by up to 90%.

The separation model predicted a BS&W of less than 0.6%. Reference: Society of Petroleum Engineers; SPE 156087 (Vessel Internal

Electrostatic Coalescer Technology (VIEC ), Ali AlQahtani, QATAR PETROLEUM)

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API 12 INSTALLATION COMPARISON WITH MODEL

Well A + Well B Mix:

Very good match between measured value and prediction by generic model for optimized separation.

Indicates that close to optimal conditions for separation are achieved at the process conditions.

BS&W [%]

Measured 18.8

Model prediction 18.9

Well A :

Generic model predicts better separation.

Indicates that there is potential for improving the separation efficiency by optimizing with respect to demulsifier type.

BS&W [%]

Measured 19.4

Model prediction 13.0

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UTILIZING ELECTROSTATIC DESTABILIZATION AS A

DEBOTTLENECKING TOOL

21 November 201218 Wrtsil

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INCREASED CAPACITY API 30

Existing test separator with diameter of 3m and a tan/tan distance of 10m.

New tie-ins from large production wells. Liquid rate: 68 MBOPD, 90 MBLPD. Bottleneck:

Test separator must be able to accommodated a whole well stream and produce as clean crude as possible: Flow measurements out from the separator will be used as calibration for the

upstream multiphase meters, which are used as fiscal instruments. Flow measurements are more accurate, the more clean the continuous phases are. The maximum allowable BS&W is therefore 5%.

21 November 2012 Presentation name / Author, Document ID:19 Wrtsil

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Shell design guide lines gives a separator with diameter of 5m and a tan/tan distance of 30m for bulk-water separation for the case production rates.

By utilizing an electrostatic destabilization in the test separator, Hamworthy-Wrtsil with the VIEC, is able to achieve a BS&W within the requirements, while keeping the existing test separator!

INCREASED CAPACITY

21 November 2012 Presentation name / Author, Document ID:20 Wrtsil

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REDUCED COST OF HEATING AND CO2 FOOTPRINT

Bottleneck: Limited space. Limited amount of gas available for heat production. Have to ship in fuel for heating.

Conventional Design Design based on VIEC Technology

Effect of VIEC Conventional With VIEC

Required Visc in Sep 15cP 30cP

Required Visc in Coal 15cP 15cP

Water Cut to Coalescer 10% 10%

Required heat duty 87.8 MW 29.0 MW

Cost of Heating $11.99m/year $3.93m/year

CO2 footprint 55 M tonn/year 18.1 M tonn/year

Natural gas: 4.55 $/MMBtu

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HOLISTIC PROCESS DESIGN

Design basis: Crude: API 14. Total liquid capacity: 180 MBLD (Arrival BS&W 33 to 83%). GOR 23-64 scf/stb. Export specification:

Crude RVP: 10 psi at 37.8 C. Crude BS&W: 0.1-0.5 %. Crude salt content: 7PTB. Produced water: 10 ppm oil.

Bottleneck: Remote location in the desert:

Electricity must be produced locally. Limited amount of gas in reservoir. Separator size must be limited due to weight limitation for transportation from yard

to site.

21 November 2012 Presentation name / Author, Document ID:22 Wrtsil

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COMPARISON

OPEX Savings

Steam cost 21.5 MUSD/year

Demulsifier 3.0 MUSD/year

Note 1 : Steam price: 20 USD/TonDemulsifier price: 0.4 USD/ppm/bld/yearElectric power: 0.12 USD/kWh

Conventional Wrtsil

Total Steam Energy Consumed [kW] 14351-48622 10378-17247

Total Heat Loss to Air [kW] 6965-29278 5166

Wash water consumption,m3/h (BWD) 21 (3168) 12 (1810)

Process train weight 472 Ton 314 Ton

Number of oil treaters required TWO ONE

CAPEX Savings

Steel cost 3.16 MUSD

Heat exchangers 1.5 MUSD

a Wrtsil company21 November 2012 Presentation name / Author, Document ID:24 Wrtsil

THANK YOU

Electrostatic destabilization of water-in-oil Emulsions:outline Separation and electrostatic destabilizationSeparation processElectro-coalescenceElectro-coalesenceBatch test example Controlling the outcomeTransport equationWrtsils flow loop rigLaboratory Multiphase PlatformSeparation modelingSeparation modelModel oil versus real crudeScaling from laboratory to full scale verificationAPI 40 installation comparison with model API 12 installation comparison with modelUtilizing electrostatic destabilization as a debottlenecking toolIncreased capacity API 30Increased capacityReduced cost of heating and CO2 footprintHolistic process designComparisonThank you