6 Chemical Flooding

Miscible and Immiscible EOR
Processes Fundamentals and

Prediction Models
Section 6 Chemical flooding
EOR Processes
Copyright Mamora & Associates
6.1
6 Chemical flooding
6.1 Micellar/polymer flooding
6.2 Alkaline flooding
6.3 Design procedures
6.4 Exercise on oil recovery with chemical flooding
EOR Processes
6.2
6.1
Micellar/polymer flooding
Process description
The process involves injecting a surfactant slug
followed by a slug of polymer solution. Surfactant
slug consists of water, surfactant, an electrolyte and
a co-solvent (alcohol). The polymer solution is
polymer-thickened water.
Process rationale
(a) Surfactant is injected to reduce oil-water IFT,
increasing the capillary number, thus decreasing
residual oil saturation. This results in improving
displacement efficiency.
(b) The polymer slug reduces mobility ratio, thus
improving volumetric sweep efficiency.
EOR Processes
6.3
Reducing IFT increases capillary number and reduces

residual oil (Stalkup)
EOR Processes
6.4
MP flooding characteristics
Micellar/polymer flooding is the EOR technique

most effective in lowering the IFT.
However, MP is the most complex EOR process.
MP flooding is also referred to as: detergent-,

surfactant-, low tension-, chemical-, and
microemulsion-flooding.
EOR Processes
6.5
Schematic diagram of micellar/polymer

process
Chase
Water
Mobility
Buffer
Slug
Preflush
Mobility buffer
Slug
Preflush
250-2500g/cm3
polymer
1-20% Surfactant
Electrolyte (Na+, Ca++,

etc.)
0-1% Alcohol
Stabilizers
Biocide
0-100% Vpf
EOR Processes
Taper
0-5% Alcohol
0-5%Cosurfactant
0-90% Oil
Sacrificial chemicals
0-100%Vpf
Polymer
5-20%Vpf
6.6
Types of surfactants
Four types of surfactants: anionic, cationic, nonionic and amphoteric.
(1) Anionic
The anionic monomer is associated with an
inorganic metal (a cation, usually sodium). The
monomer molecule dissociates in aqueous solution
into free cations (positively charged), and anionic
monomer (negatively charged). Anionic surfactants
are the most common in MP flooding because they
are good surfactants, relatively resistant to
retention, stable, and can be made relatively cheap.
EOR Processes
6.7
(2) Cationic
The cationic surfactant molecule contains an inorganic
anion to balance the charge. In solution it ionizes into
a positively charged monomer, and the anion. Cationic
surfactants are readily adsorbed by clays and thus not
used in MP flooding.
(3) Non-ionic
This class of surfactant does not have ionic bonds.Nonanionic surfactants are much more tolerant to high
salinities than anionic, but they are poorer surfactants.
The non-ionic surfactants are used extensively in MP
floods mainly as co-surfactants.
EOR Processes
6.8
(4) Amphoteric
This surfactant contains characteristics of two or more
of the previous classifications and therefore has not
been used for EOR processes.
EOR Processes
6.9
Summary of surfactant types

-
Anionics
Cationics
Noionics
Amphoterics
Quaternary ammonium
Alkyl-, alkyl- aryl-,
organics, pyridinum,
Aminocarboxylic
acyl-, acylamindoimidazonlinium,
acids
acyl- aminepolyglycol,
piperidinium, and
and polyol ethers
sulfononium compounds
Sulfonates,
Sulfates,
Carboxylates,
Phosphates
O
C
C
C
C
C
C
C
C
O -Na +
(a) Sodium dodecyl sulfate

C
C
C
C
C
C
C
C
C
C
C
C
C
O
S
O - Na +
(b) Texas No. 1 sulfonate

O
R
O - Na +
EOR Processes
6.10
Critical micelle concentration

Micelles
Surfactant Monomer
Concentration
Monomers
Critical Micelle
Concentration
(CMC)
Total Surfactant Concentration
Typical CMC values are 10-5 10-4 kg-mol/m3.

Size of micelles is 10-4 to 10-6 mm.
EOR Processes
6.11
Surfactant-brine-oil phase behavior
WATER
OIL
WATER
(W)
MOLECULAR
DISPERSION
IN WATER
EOR Processes
OIL
WATER
(S1)
(S2)
WATER
EXTERNAL
OIL
EXTERNAL
(O)
MOLECULAR
DISPERSION
IN OIL
6.12
Ternary diagram to represent

surfactant/oil/brine phase behavior
EOR Processes
6.13
Numbering of phases and species
Species
Concentration Unit
Phase
Water
Volume Fraction
Aqueous
Oil
Volume Fraction
Oleic
Surfactant
Volume Fraction
Microemulsion
Polymer
Weight percent or g/m3
EOR Processes
6.14
Type II (-) behavior
At low brine salinity, a typical MP surfactant will

exhibit good aqueous phase solubility.
Oil occupies the central core of the swollen
micelles.
The tie lines within the 2-phase envelope have a
negative slope.
The plait point PR in this system is located closer
to the oil apex.
EOR Processes
6.15
Type II (-) behavior
EOR Processes
6.16
Type II (+) behavior
EOR Processes
6.17
Type III behavior
EOR Processes
6.18
Simplified phase diagram for microemulsion

system
EOR Processes
6.19
Changes in phase conditions

Changing any condition besides salinity - that
enhances the surfactants oil solubility will usually
cause a shift from type II (-) to type II (+). These
conditions include:
Decreasing temperature
Increasing surfactant molecular weight
Decreasing oil specific gravity
Increasing concentration of high molecular weight
alcohols.
Decreasing surfactants oil solubility will cause the
reverse change
EOR Processes
6.20
Pseudoternary or tent' diagrams of micellarpolymer phase behavior
EOR Processes
6.21

Alkaline flooding is also known as caustic flooding. It
is a high pH chemical EOR method which has many
similarities with micellar flooding. The difference is
that in micellar flooding the surfactant is injected,
while in alkaline flooding the surfactant is generated
in situ.
EOR Processes
6.22

High pHs indicates large concentrations of hydroxide
anions COH-. The pH of an ideal aqueous solution is
defined as:
pH = log C H +
kw =
EOR Processes
C OH C H +
C H 2O
6.23
Controlling pH
There are two methods for increasing the pH of a
reservoir fluid:
(1) By dissociation of a hydroxyl containing
species such as NaOH, or KOH.
(2) By adding chemicals that will bind with CH+.
EOR Processes
6.24
Sources of OHSodium hydroxide or sodium carbonate dissociates in

water following the dissociation reactions:
2
Na2CO3 CO3 + 2 Na
CO3
+ 2H 2O H 2CO3 + 2OH
NaOH Na
EOR Processes
+ OH
6.25
Surfactant formation
OH - by itself is not a surfactant since the absence of a

lypophilic tail makes it exclusively water soluble.
However, if the oil contains acidic hydrocarbon
components (HAo), some of it may partition into the
aqueous phase.
EOR Processes
6.26
Schematic diagram of alkaline flood recovery

H2O
OH-
ROCK
A-
Na+
HAo
OIL
HAo
HAw
EOR Processes
H
NaOH
A- + H+
H2O
6.27
Oil requirements
If no acidic species are present in the crude, no

surfactant can be generated.
To determine the oil characteristics needed for
alkaline flooding we must characterize its acidity.
EOR Processes
6.28
Acid number
The acid number is the milligrams of potassium
hydroxide (KOH) needed to neutralize one gram
of crude oil.
The acidic species HAo is removed from the crude
oil to the aqueous phase
The aqueous phase is brought to neutral pH=7 by
adding KOH.
EOR Processes
6.29
Useful considerations
For a meaningful value, the oil must be free of acidic
additives such as corrosion inhibitors and acidic
gases such as H2S and CO2.
A good alkaline flooding candidate will have an acidic
number of 0.5 mg/g or greater.
EOR Processes
6.30
SPE DISTINGUISHED LECTURER SERIES

is funded principally
through a grant of the
SPE FOUNDATION
The Society gratefully acknowledges
those companies that support the program
by allowing their professionals
to participate as Lecturers.
And special thanks to The American Institute of Mining, Metallurgical,
and Petroleum Engineers (AIME) for their contribution to the program.
EOR Processes
6.31
Chemical EORThe Past,

Does It Have A Future?
Sara Thomas
PERL Canada Ltd
STSAUS@aol.com
EOR Processes
6.32
The Past :
Limited Commercial Success
FUTURE: Very Bright
Past experience
High oil prices
Scaled models
EOR Processes
6.33
Objectives
Why chemical EOR methods have not been
successful?
Process limitations
Current status of chemical floods
Recent changes that make such methods
attractive
EOR Processes
6.34
Chemical EOR Holds A Bright Future

Conventional oil RF <33%, worldwide
Unrecoverable oil = 2x1012 bbls
Much of it is recoverable by chemical methods
Chemical methods are attractive:
Burgeoning energy demand and high oil prices,
most likely for the long-term
Diminishing reserves
Advancements in technologies
Better understanding of failed projects
EOR Processes
6.35
Chemical EOR Target in Selected

Countries
173
160
Assumed:
Primary Rec. 33.3 %OOIP
Chem. Flood Rec. 33.3 %OIP
120
100
100
84
80
77
63 61
60
51
40
40
EOR Processes
India
UK
3 0.9
0.6 0.3 0.2
France
Germany
Romania
Denmark
Dubai
Oman
Mexico
Qatar
Nigeria
Libya
Russia
Venezuela
Abu Dhabi
Kuwait
Iraq
USA
S. Arabia
Iran
12 10 10 9
Norway
20
Brazil
26 24
China
Billion Bbls
140
Canada
180
6.36
Chemical EOR Target in Selected

Countries
10
173100 84 77 63 61 51 40 26 24 12 10 10
Assumed:
Primary Rec. 33.3 %OOIP
Chem. Flood Rec. 33.3 %OIP
7
6
7
6
5
4
3
EOR Processes
Dubai
UK
India
Oman
Norway
Brazil
Canada
Mexico
Qatar
China
Nigeria
Libya
Russia
Venezuela
Abu Dhabi
Kuwait
Iraq
USA
S. Arabia
Iran
0.9
0.6
0.3 0.2
France
2
1
Germany
Romania
4
3
Denmark
Billion Bbls
9
8
6.37
Chemical Methods
Chemical EOR methods utilize:
Polymers
Surfactants
Alkaline agents
Combinations of such chemicals
ASP (Alkali-Surfactant-Polymer) flooding
MP (Micellar-Polymer) flooding
EOR Processes
6.38
Classification
CHEMICAL METHODS
Alkali
Surfactant
Polymer
EOR Processes
Micellar
Emulsion
ASP
6.39
Chemical Floods History

USA
CHINA
300,000
Total
25,000
Oil Production, B/D
Oil Production, B/D
Total
20,000
15,000
10,000
5,000
Polymer
Micellar
Surfactant
250,000
200,000
150,000
100,000
Alkaline
19
78
19
80
19
82
19
84
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
EOR Processes
50,000
1995
1997
1999
2001
2003
6.40
Chemical Floods - Current Status

Worldwide
Indonesia
Venezuela
USA
India
France
China
Total Number of Projects: 27

OGJ April 12, 2004
EOR Processes
6.41
Chemical Floods - Production

Worldwide
France
Indonesia
USA
China
Total oil production: 300,000 B/D

OGJ April 12, 2004
EOR Processes
6.42
Objectives of Chemical Flooding

Increase the Capillary Number Nc to mobilize
residual oil
Decrease the Mobility Ratio M for better sweep
Emulsification of oil to facilitate production
EOR Processes
6.43
Chemical Flooding - General

Limitations
Cost of chemicals
Excessive chemical loss: adsorption, reactions
with clay and brines, dilution
Gravity segregation
Lack of control in large well spacing
Geology is unforgiving!
Great variation in the process mechanism, both
areal and cross-sectional
EOR Processes
6.44
Polymer Flooding
Loss to rock by adsorption, entrapment, salt
reactions
Loss of injectivity
Lack of control of in situ advance
High velocity shear (near wellbore), ageing, crosslinking, formation plugging
Often applied late in waterflood, making it largely
ineffective
mixing zone
drive
water
polymer slug
residual oil
water
oil
Polymer Flood
EOR Processes
6.45
Polymer Flood - Field Performance

Sanand Field, India
125
650
100
620
EOR OIL
75
Projected
590
50
560
25
530
0
1989
EOR Processes
500
1991
1993
1995
6.46
Polymer Flood Field Projects

Project
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Taber Manville South

Pembina
Wilmington
East Colinga
Skull Creek South
Skull Creek Newcastle
Oerrel
Hankensbuettel
Owasco
Vernon
Northeast Hallsville
Hamm
Sage Spring Cr. Unit A
West Semlek
Stewart Ranch
Kummerfeld
Huntington Beach
North Stanley
Eliasville Caddo
North Burbank
EOR Processes
Flood Type Formation Polymer Rec., %OIP

Secondary
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
Tertiary
Tertiary
Tertiary
Sandstone
"
"
"
"
"
"
"
"
"
Carbonate
Sandstone
"
"
"
"
"
"
Carbonate
Carbonate
PAA
"
"
Biopolymer
PAA
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
2
0
0
0
8
10
23
13
7
30
13
9
1.2
5
8
6
4
1.1
1.8
2.5
6.47
Surfactant Flooding
Variations
Surfactant-Polymer Flood (SP)
Low Tension Polymer Flood (LTPF)
Adsorption on rock surface
Slug dissipation due to dispersion
Slug dilution by water
mixing zone
Formation of emulsions
drive
Treatment and disposal
polymer slug
water
problems
residual oil
water
oil
Polymer Flood
EOR Processes
6.48
Surfactant Flood -Field Performance

Glenn Pool Field, OK
OIL
1,000
100
WOR
10
1984 85
EOR Processes
86
87
88
89
90
91 92
6.49
Alkaline Flooding
Process depends on mixing of alkali and oil
Oil must have acid components
Emulsification of oil, drop entrainment and
entrapment occur
Effect on displacement and sweep
efficiencies?
Polymer slugs used in some cases
Polymer alkali reactions must be accounted
for
mixing
zones
Complex process to design
low
caustic IFT
slug zone
drive
water
water
oil
residual oil
Alkaline Flood
EOR Processes
6.50
Alkaline Flooding
Field Performance
Field
Slug Size Conc. Oil Satn. Consum. Oil Rec.

% PV
wt%
%PV mg/g rock %OIP
1 Whittier
8
0.2
51 2.4-11.2
4
2 Singleton
8
2.0
40
5
3 N. Ward Estes
15
4.9
64
17.2
8
4 L. A. Basin
5
0.4
30
3
5 Orcutt Hill
2
0.42
50
0.5
2
6 Van
12
0.14
25-35
0.6-1.2
3
7 Kern River
48
0.15
52
1.3
none
8 Harrisburg
9
2.0
30-40
6
9 Brea-Olinda
1.2
0.12
50-60
2
EOR Processes
6.51
Alkaline-Polymer Flood
David Field, Alberta
100
1000
Oil Cut
100
10
10
Oil Rate
1
Waterflood
Alkaline-Polymer
Flood
Primary
1
0.1
1969 1974 1979 1984 1989 1994 1999 2004
EOR Processes
6.52
ASP: Alkali-Surfactant-Polymer Flooding
ASP
SAP
PAS
Sloppy Slug
polymer
alkali
drive
water
Surf
Several variations:
oil water
bank
oil
ASP Flood
Injected as
premixed slugs
or in sequence
Field tests have been encouraging

Successful in banking and producing residual oil
Mechanisms not fully understood
EOR Processes
6.53
ASP Pilot Daqing, China

100
Oil Rate
50
Oil Cut
20
10
1993
EOR Processes
1994
1995
1996
6.54
Micellar Flooding
Utilizes microemulsion and polymer buffer slugs

Miscible-type displacement
Successful in banking and producing residual oil
Process limitations:
Chemical slugs are costly
Small well spacing required
High salinity, temperature and clay
Considerable delay in response
Emulsion production
Micellar Flood
polymer
drive
water
mixing
zone
micellar
slug
EOR Processes
water
oil
bank
oil
mixing zone
6.55
ASP vs. Micellar Flood -Lab Results

Mitsue Oil Core Floods
ASP Flood
Micellar Flood
Oil Cut,%; Cum. Recovery,% OIP
100
100
Slug 5% Buffer 50%
80
92% OIP
80
Soi 32%
60
Alkali 5%,Surfactant 10%,Polymer 60%

Soi 38%
80% OIP
60
40
40
Oil Cut
20
20
0
0
0.5
1.5
Pore Volumes Injected
2.5
Oil Cut
0.5
1.5
2.5
Pore Volumes Injected
Earlier oil breakthrough and quicker recovery in micellar flood

EOR Processes
6.56
Micellar Flood Typical Performance

Bradford Special Project No. 8
10
1,000
Oil Cut
1
100
Oil Rate
10
Dec. 81 Dec. 82
Dec. 83
Dec. 84
Dec. 85
0.1
micellar
injection
EOR Processes
6.57
Micellar Flood Field Tests

100
Henry S
Henry E & Henry W
80
119-R
Wilkins
60
40
Dedrick
20
0
10
12
14
Micellar Slug Size, %PV

EOR Processes
6.58
ASP and MP Field Projects

ASP Floods
Started Appln.
Acre Rec., %OIP
David, Alberta
1986 Tertiary
252
*21
West Kiehl, Wyoming
1987
"
106
34.4
Gudong, China
1992
"
766
29.4
Cambridge, Wyoming
1993
"
72
*26.8
Daqing, China
1994
"
8.4
23.9
Karamay, China
1996
"
766
*24
Viraj, India
2002
"
68
*24
Micellar Floods
Dedrick (IL)
1962 Secondary
2.5
*49.7
Robinson, 119-R (IL)
1968 Tertiary
40
39
Benton (IL) Shell
1972
"
160
29
Robinson, 219-R (IL)
1974
"
113
27
North Burbank (OK)
1976
"
90
11
Robinson, M1 (IL)
1977
"
407
50
Bradford (PA)
1980
"
47
50
Salem Unit (IL)
1981
"
200
47
Louden (IL)
1977
"
40
27
Louden (IL)
1980
"
80
33
Chateaurenard, (France)
1983
"
2.5
67
* %OOIP
EOR Processes
6.59
Other Methods
Emulsion flooding
Micellar-Alkaline-Polymer flood (MAP)
ASP-Foam process
Surfactant huff npuff
Surfactant with thermal processes
EOR Processes
6.60
Reasons for Failure

Low oil prices in the past
Insufficient description of reservoir geology
Permeability heterogeneities
Excessive clay content
High water saturation
Bottom water or gas cap
Fractures
Inadequate understanding of process
mechanisms
Unavailability of chemicals in large quantities
Heavy reliance on unscaled lab experiments
EOR Processes
6.61
Scale-Up Methods
Require:
Knowledge of process variables or complete
mathematical description
Derivation of scaling groups
Model experiments
Scale-up of model results to field
Greater confidence to extend lab results to field
EOR Processes
6.62
Scaling Groups
Micellar Flood:
L
d
gh
o
Soi o L2
kkromax pt
PcLEmax
o gh
PcLE
max
P
cEAmax
qL* o L2
kkromax p
krwmax o
kromax w
Soi KLo
kkromax p
KL

KT
krEmax w
krwmax E
q*A
*
qL
Cs
S
C
oi o L,s
qE*
*
qL
Cs

Cp
Additional Groups:
Slug Size, Flood Rate, Mixing Coefficient, Oil
Recovery
Soi p
( PV)Sp = ( PV)sM
SoiM
EOR Processes
kp
vp = vM
km
Soi
p = M aM
S
oip
rP =
SoiM (1rM )
SoiP
6.63
Results: Prediction vs. Actual
Oil Recovery, %OIP
60
Actual
50
40
30
Predicted
20
10
0
0
0.2
0.4
0.6
0.8
1.2
Pore Volumes Produced
EOR Processes
6.64
Chemical EOR & Heavy Oil

Applicable methods:
Surfactant flooding unsuccessful
Alkaline flooding
unsuccessful
CO2 immiscible; cyclic stimulation Limited
success with WAG
Problems:
Unfavourable mobility ratio
Rock-fluid reactions, chemical loss, dilution
Lack of scaling criteria, inadequate simulation
Often used where steam is not suitable
Gravity segregation
EOR Processes
6.65
EOR Screening Criteria

Most important: geology and mineralogy
Oil viscosity < 35 cp

Oil API gravity > 30 API
Permeability 100 md
Porosity
15%
Temperature < 150 F
Depth
< 9,000 ft
Pressure
not critical
Oil saturation 45%
Oil in place at process
start 600 Bbl/acre-ft
EOR Processes
Formation sdst preferred

Thickness
20-30 ft
Stratification desirable
Clay content
< 5%
Salinity < 20,000 ppm
Hardness
< 500 ppm
Oil composition Light,
intermediates & organic
acids desirable
No bottom water or gas
cap
6.66
How To Plan a Flood

Choose a process likely to succeed in a candidate
reservoir
Determine the reasons for success or failure of
past projects of the process
Research to fill in the blanks
Determine process mechanisms
Derive necessary scaling criteria
Carry out lab studies
Field based research
Establish chemical supply
Financial incentives essential
EOR Processes
6.67
Process Evaluation
Compare field results with lab (numerical)
predictions
Relative permeability changes?
Oil bank formation? If so, what size?
Mobility control?
Fluid injectivity?
Extent of areal and vertical sweep?
Oil saturations from post-flood cores?
EOR Processes
6.68
Interpretation of Results
Large number of chemical floods with little
technical success
Field tests implemented for tax advantage
misrepresent process performance
Questionable interpretations distort process
potential
EOR Processes
6.69
Cost of Chemicals
As oil prices rise, so does cost of chemicals, but
not in the same proportion
Typical Costs:
Polymer
- $3/lb
Surfactant
- $1.20/lb
Crude oil
- $60/bbl
Caustic - $0.60/lb
Isopropanol - $20/gallon
Micellar slug - $25/bbl
Process Efficiency: volume of oil recovered per

unit volume (or mass) of chemical slug injected
EOR Processes
6.70
The Case for Chemical Flooding

Escalating energy demand, declining reserves
Two trillion bbl oil remaining, mostly in depleted
reservoirs or those nearing depletion
Infill drilling often meets the well spacing required
Fewer candidate reservoirs for CO2 and miscible
Opportunities exist under current economic
conditions
Improved technical knowledge, better risk
assessment and implementation techniques
EOR Processes
6.71
Conclusions
Valuable insight has been gained through
chemical floods in the past failures as well as
successes
MP and ASP methods hold the greatest potential
for commercial success; polymer flooding a third
option
Chemical flooding processes must be
re-evaluated under the current technical and
economic conditions
EOR Processes
6.72
Conclusions
Chemical floods offer the only chance of
commercial success in many depleted and
waterflooded reservoirs
Chemical flooding is here to stay because it holds
the key to maximizing the reserves in our known
reservoirs
EOR Processes
6.73

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6 Chemical Flooding

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Miscible and Immiscible EOR

Processes Fundamentals and

Copyright Mamora & Associates

Copyright Mamora & Associates

Copyright Mamora & Associates

Reducing IFT increases capillary number and reduces

Copyright Mamora & Associates

Micellar/polymer flooding is the EOR technique

However, MP is the most complex EOR process.

MP flooding is also referred to as: detergent-,

Copyright Mamora & Associates

Schematic diagram of micellar/polymer

Electrolyte (Na+, Ca++,

Copyright Mamora & Associates

Copyright Mamora & Associates

Copyright Mamora & Associates

Copyright Mamora & Associates

Summary of surfactant types

(a) Sodium dodecyl sulfate

(b) Texas No. 1 sulfonate

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Critical micelle concentration

Total Surfactant Concentration

Typical CMC values are 10-5 10-4 kg-mol/m3.

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Surfactant-brine-oil phase behavior

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Ternary diagram to represent

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Numbering of phases and species

Weight percent or g/m3

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Type II (-) behavior

At low brine salinity, a typical MP surfactant will

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Type II (-) behavior

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Type II (+) behavior

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Type III behavior

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Simplified phase diagram for microemulsion

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Changes in phase conditions

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Pseudoternary or tent' diagrams of micellarpolymer phase behavior

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6.2 Alkaline flooding

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6.2 Alkaline flooding

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Sources of OHSodium hydroxide or sodium carbonate dissociates in

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OH - by itself is not a surfactant since the absence of a

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Schematic diagram of alkaline flood recovery

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If no acidic species are present in the crude, no

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