Challenges of Desalting Canadian Crudes Sams

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Challenges of Desalting Canadian CrudesGary W. Sams

Director R&D

Heavy Oil PFD

Crude Oil Quality Association

FWKO

Separator

Treater

• Oil lighter than water• High inlet water cut• Oil internal• Temperatures < 143 C 25% Oil

75% Water 65% Water

72% Oil28% Water 20% Water

9% Water90% Oil10% Water

99% Oil1% Water

• Smaller water drops• Shifted to oil external

• Smallest water drops• Mostly emulsified• Solids stabilized

Gas

Gas

Degassing / Dehydration


Inlet

Gas Oil

Water Water

HiFlo Spreader

Collector

Electrodes

Dual Frequency

Cyclonic Gas Removal



2)K( Rate Settling gdow

Temperature vs. Viscosity

Chemical Treatment

Program

Stoke’s Law dEc

Emulsifying Factors

Water Solubility

4

62

drKEFcoalescing

Desalter Design Issues

Solids & Oil in Effluent

Small micron particulates,crystalline salt, and heavy solids loads


Substantial asphaltene precipitation

Reverse Emulsion


16 API SAGD DilBit

Dro

plet

Pop

ulat

ion,

%

0 50 100 150 200 250 300 350 400 450 500 550 600Droplet Diameter, microns

0

10

20

30

40

50

Final Droplet Distribution

Initial Droplet Distribution

Water Droplet Growth


Kuwait Oil - 25ºAPI

Chemical

Bottle Test Electrostatic Bench Test

Water in Oil% By Difference

BS&WMeasured %

Brand A 3.6 1.4Brand B 4.0 1.51Brand C 4.8 1.51Brand D 5.5 0.7

Best Performance

Best Performance

Based on lab tests – Initial BS&W – 10%Crude Oil Quality Association

Demulsifier Selection

Electrostatic Field Selection

Our Choices Include…• AC – Conventional & Deep-Field• DC Only (with refined products)• Dual Polarity® - Combination AC/DC• Modulated Dual Polarity®

• Electro-Dynamic Desalting®

• Dual Frequency®


AC Electrostatic Forces


Positive Forces& Velocities

Negative Forces& Velocities

Electrostatic Voltage Field, V/ m

Vertical oil velocity, vv

Droplet Radius, rDrop Spacing, S

DropletWeight, WD

Elec

trod

e #1

Elec

trod

e #2

DipoleForceDrop

Velocity

DragForce

DC Electrostatic Forces







DropletWeight, WD

Elec

trod

e #1

Elec

trod

e #2

ElectrophoresisForce

DropVelocity

DragForce

Gradient Electrostatic Forces







DropletWeight, WD

Elec

trod

e #1

Elec

trod

e #2

Di-electrophoresisForce


DropVelocity

DragForce

Net Electrostatic Forces







DropletWeight, WD

Elec

trod

e #1

Elec

trod

e #2

DipoleForce

ElectrophoresisForce



DropVelocity

DragForce

Viscous Drag

Weight

Dipolar AttractionElectrophoretic

Force

++ --Vol

ts

Voltage FieldDipole Electrophoretic

Direction Force Direction ForceAlternating Current Oscillates 0.4 weight Reverses Net is zeroDirect Current Constant 0.4 weight Constant 7230 weight

+

Volts

-

Electrostatic CoalescenceNet Drop Forces in Voltage Field


} Bulk Water Removal

AC/DC Electrostatic Field


Oil

Flux

Desalter Hydraulic Efficiency


Excessive Oil Conductivity


0200400600800

10001200140016001800

50 100 150 200 250 300

Temperature, F

Cond

uctiv

ity, n

S/m Typical

High

Heavy Oil Dehydrator PerformanceRef: SPE Paper 97786


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

Oil Flux (bopd/sf)

Out

let B

S&W

(%)

Field AC Dehydrator @ 239 F

AC Dehydrator @ 219F

AC/DC @ 218F

Modulated AC/DC @ 220F

Bimodal AC/DC @ 220F

Solid Curves Predicted by Electrostatic Dehydrator Computer Model

AC Dual PolarityDual

Frequency

ModulatedDual

Polarity

Oil API – 21TAN - 4

Technology RetrofitA Commercial Installation

Before Retrofit* After Retrofit*Technology: Dual Polarity Dual FrequencyTemperature: 220ºF 200ºFOil Flow: 4000 BOPD 9200 BOPDOutlet BS&W: 1% 0.1%

*Data is per vessel. There are four vessels.


Gravity = 12ºAPI

SAGD -Dilbit Desalting Pilot Results

Process Parameters:Dilbit API: 16 , Temp: 280F, Flux: 70 bopd/ft2

Stage Tech.Feed Outlet

BS&W, % Salt, ppm Cl- BS&W, % Salt, ppm Cl-

1 AC 5.8 220 0.4 6

Wash Water: 5 % Recycle: 5 % Valve DP: 10 psi

2 DF 0.4 6 0.35 1

Mixing Efficiency = 25%


Desalter Technology Comparison InletSalt

OutletSalt

BSW

AC 258 41 0.5

AC‐pAC

258 12 0.4

DF 211 6.3 0.4

EDD‐EDD

200 3.2 0.4

DF‐DF 210 2.8 0.3

EDD‐DF

200 2.4 0.3

DF‐EDD

210 2 0.4


ConclusionsHeavy Canadian crudes pose unique challenges:

• High Oil Conductivities• Asphaltene Precipitation• High Solids Loading• Reverse Emulsions• Increased Interface Rag• Poor Effluent Water Quality


Challenges of Desalting Canadian Crudes Sams

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