natco study on new technology in desalters
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Advanced
Electrostatic
Technology for
Heavy Oils
May 2009
AGENDA
• Opportunity Crude Issues
• Electrostatic Technology
• Desalting Technology
• Dual Frequency® Dehydration
• Experience with Heavy Crudes
Heavy Crude Issues
Difficult-to-Treat Oils
The Bad Actors…
• Electrical Conductivity
• Interfacial Tension
• Reverse Emulsions
• Limited Differential Density
• High Solids• Asphaltenes
• Sands, Scale
• Crystalline Salts
Excessive Oil Conductivity
0
200
400
600
800
1000
1200
1400
1600
1800
50 100 150 200 250 300
Temperature, F
Co
nd
ucti
vit
y,
nS
/m Typical
High
Interfacial Tension
Platinum Ring Tensiometer
• At Ambient Temperature– 15 -25 dynes/cm
• At Treating Temperature– 10 – 15 dynes/cm
• With Demulsifier– 7 – 10 dynes/cm
• In Electrostatic Field– 3 – 5 dynes/cm
Water-in-Oil Emulsion
Typical
Reverse Emulsion
16 API SAGD DilBit
Crystalline Salt
A Vexing Problem…
Dissolved Salt
Dry Salt Crystals
+
+
+
-
-
-
Na+H2O
H2O
H2O
H2O
H2OCl-
NaCl
Na+ Cl-NaCl
NaCl
NaCl
Salt Crystals Associated With Brine
Electrical Forces
Water-in-Oil Emulsion
with Salt Crystal
Crystalline Salt
Electrostatic
Technology
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®
Electrostatic Fields
Electrostatic Dehydrators
Net Drop Forces in Voltage Field
Viscous Drag
Weight
Dipolar
AttractionElectrophoretic Force
++ --
Volts
Voltage Field
Dipole Electrophoretic
Direction Force Direction Force
Alternating Current Oscillates 0.4 weight Reverses Net is zero
Direct Current Constant 0.4 weight Constant 53 weight
Electrode
} Bulk Water
Removal
Dual Polarity®
AC/DC Electrostatic Field
Dual Polarity®O
il F
lux
Desalting
Technology
Electrostatic Desalter
Single Stage Flow Diagram
Mixing
Valve
Effluent
PumpDilution
Water
Feedstream
Oil Outlet
Water ToDisposal
Electrostatic
Desalter
to HEX
Electrostatic Desalter
Two Stage Flow Diagram
Mixing
Valve
Effluent
Pump
Feedstream
Water ToDisposal
Electrostatic
Desalter
Mixing
Valve
Effluent
PumpDilution
Water
Oil Outlet
Electrostatic
Desalter
to HEX
InterstageRecycle
Electrostatic Desalter
Essential Components:
1. Mixing
3 – 6% water up to 15 psi DP
2. Internal Recycle
From 5 to 10% of crude rate
3. Electrostatic Field
Target oil viscosity is 5 to 10 cP
4. Enhanced Distribution / Collection
Maximum vessel utilization
Dual Frequency
Dehydration
Oil Conductivity
Effects on Voltage Decay
Low Medium High
Thre
sh
old
Vo
ltag
eV
olta
ge
Oil Conductivity
Insta
nta
neous V
oltage
High Oil Conductivity
Frequency Effect on Voltage Decay
Low Frequency High Frequency Thre
shold
Volta
ge
Voltag
e
Time
Avera
ge F
ield
Str
ength
Instantaneous Voltage
Dual Frequency Waveform
Coupled with Voltage Modulation
-600
-400
-200
0
200
400
600
Time
Pri
ma
ry V
olt
ag
e, v
olt
s
Base
Frequency
Modulation
Frequency
Threshold
Voltage
12 - 25 kV
Sinusoidal Wave
(or trapezoidal,
triangular, square,
etc)
Droplet
charge follows
the Modulation
waveform
Critical
Voltage
20 - 40 kV
System Performance:
1. High Conductance Crudes
High (base) frequency
2. Water Drop Interfacial Tension
Low (pulse) frequency
3. Combined to achieve
Lowest Salt and BS&W
Dual Frequency Dehydrator
Heavy Oil
Performance
Technology Comparison
Pilot Results
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)
Ou
tle
t 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
Modulated
Dual
Polarity
Oil API – 21
TAN - 4
Ref: SPE Paper 97786
Technology Comparison
Heavy Oils
Pilot / Field Tests
Increased Oil Flux
Flux (BOPD/ft2)@ BS&W Oil Gravity
ºAPI Dual Polarity Dual Frequency
Comments
16 100 @ 0.63% 125 @ 0.56% Diluted SAGD, Canada
20.2 90 @ 0.38% 220 @ 0.4% West Sak, Alaska
20.7 90 @ 0.35% 175 @ 0.4% Bohai, China
24 125 @ 0.4% 208 @ 0.4% Venezuela
Advanced Dehydration Results
Dual Polarity vs. Dual Frequency
Pilot data on several oils from 13.8 to 25 API.
Dual
Polarity
1.78
0.3
1.45
1.35
0.5
0.9
Dual
Frequency
0.6
0.1
0.85
0.8
0.27
0.55
Outlet BS&W (%)
Venezuela
Venezuela
Wyoming
Oklahoma
Brazil
North Sea
Crude
Identification
25
17
24
22.8
13.8
20.8
Crude API
9
28
11
11
5
Feed
BS&W
(%)
200
94
100
75
80
150
Grid Load
(bopd/sf)
150
280
130
135
240
Temperature
(F)
200
Heavy Oil Desalting
Pilot Results
• Dilbit API - 16
• Temperature - 280 F
• 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
2 DF 0.4 6 0.35 1
• Wash Water – 5 %
• Recycle – 5 %
• Valve DP – 10 psi
Mixing Efficiency = 25%
Crystalline Salt Removal
Aggressive Mixing
• WCS Crude - 20 API
• Average Inlet Salt Is 10 ptb
• Flux Rate of 115 bpd/sf @ 280 F
• 5% fresh water
3 Static + Valve Deep-field AC 0.6 2.2
3 Static + Valve Dual Polarity 0.4 1.3
3 Static + Valve Dual Frequency 0.15 0.5
Dynamic Dual Frequency 0.3 1
Mix TechnologyElectrostatic
Technology
BS&W
%
NaCl
ptb
Mixing Efficiency = 40%
Questions?
Heavy Oil Technology for
Offshore Applications
May 2009
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