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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
Crude Oil Quality Association
Inlet
Gas Oil
Water Water
HiFlo Spreader
Collector
Electrodes
Dual Frequency
Cyclonic Gas Removal
Crude Oil Quality Association
Crude Oil Quality Association
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
Crude Oil Quality Association
Substantial asphaltene precipitation
Reverse Emulsion
Crude Oil Quality Association
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
Crude Oil Quality Association
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®
Crude Oil Quality Association
AC Electrostatic Forces
Crude Oil Quality Association
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
Crude Oil Quality Association
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
ElectrophoresisForce
DropVelocity
DragForce
Gradient Electrostatic Forces
Crude Oil Quality Association
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
Di-electrophoresisForce
Di-electrophoresisForce
DropVelocity
DragForce
Net Electrostatic Forces
Crude Oil Quality Association
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
DipoleForce
ElectrophoresisForce
Di-electrophoresisForce
Di-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
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} Bulk Water Removal
AC/DC Electrostatic Field
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Oil
Flux
Desalter Hydraulic Efficiency
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Excessive Oil Conductivity
Crude Oil Quality Association
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
Crude Oil Quality Association
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.
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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%
Crude Oil Quality Association
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
Crude Oil Quality Association
ConclusionsHeavy Canadian crudes pose unique challenges:
• High Oil Conductivities• Asphaltene Precipitation• High Solids Loading• Reverse Emulsions• Increased Interface Rag• Poor Effluent Water Quality
Crude Oil Quality Association