salt tolerant synthetic polymers effects on adsorption and retention masoud rashidi sigmund sandvik...
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Salt Tolerant Synthetic PolymersEffects on adsorption and retention
Masoud RashidiSigmund Sandvik
Anne Marit BlokhusArne Skauge
Presented by Ketil Djurhuus
IEA Collaborative Project on EOR30th Annual Workshop and Symposium
21-23 September, Canberra, Australia
Outline
• Introduction and motivation• Materials and experiments• Static and dynamic retention• Practical applications • Conclusions
Why polymer flooding?
1. Improve area sweep
2. Reduce viscous fingering
Before polymer flooding After polymer flooding
High mobility ratio Low mobility ratio
Limitations of conventional polymers
Salinity (w
t.%)
10
5
20
0 50 100 150Temperature (°C)
Xanthan
HPAM
Effects of polymer adsorption and retention
• Polymers accumulate adsorb at the solid/liquid interface.
• Polymer injection reduces permeability due to retention of polymer by adsorption and mechanical entrapment.
• Loss of polymer due to retention causes lower viscosity of fluid.
Materials• HPAM little salt tolerant
• Sulfonated copolymers have improved solution properties
• Sulfonation improves salt tolerance compared to carboxylates
• Sulfonated polymers areless prone to precipitation
Hydrolyzed polyacrylamide
Sulfonated polyacrylamide
Experimental plan
Polymers HPAM
AN 105 AN 113 AN125 AN 132
Sulfonation degree (mole %)
0 51 13 25 32
Polymers AN 125 VLM
AN125 AN125 VHM
Mw (MDalton)
2 8 12
Varying sulfonation degree Molecular weight = 8 MDalton
Varying molecular weight Sulfonation degree = 25 mole%
1 Molecular weight = 6 MDalton
Experiments
• Static adsorption– Two different minerals e.g. kaolinite and silica– Constant solid/liquid ratio to avoid flocculation.
• Dynamic retention– Berea outcrop sandstone– Injection of two pore volumes polymer with known
concentration followed by 3 pore volumes solvent– Tracer injected along with the polymer to detect any
difference in flow pattern
Static adsorption Adsorption isotherm on kaolinite. SD= 13% Mw = 8 MDalton
S/L= 0.005, T = 20C, Salinity = 5 wt% NaCl
0
100
200
300
400
500
600
700
800
0 50 100 150 200 250 300
Equilibrium concentration [ppm]
Ad
sorp
tio
n [
µg/m
2]
Static adsorption: Effect of sulfonationMw = 8 MDalton
S/L= 0.005, T = 20C
0
200
400
600
800
1000
1200
1400
1600
0 4 8 12 16 20 24 28 32 36
Sulfonation Degree [mole %]
Ad
sorp
tio
n [
μg
/m2]
SSW
5 w t% NaCl
HPAM
Static adsorption: Effect of molecular weightSulfonation degree = 25%
S/L= 0.005, T = 20C
0
200
400
600
800
1000
1200
1400
1600
0 2 4 6 8 10 12 14
Molecular weight [MDa]
Ad
sorp
tio
n [
μg
/m2]
SSW
5 w t% NaClHPAMHPAM
Dynamic retentionDynamic retention profile on a Berea core. SD= 25%
Mw = 12 MDalton. T = 20C. Salinity = SSW
Dynamic retention: Effect of sulfonationMw = 8 MDalton
T = 20C
0
20
40
60
80
100
120
140
0 4 8 12 16 20 24 28 32 36
Sulfonation Degree [mole %]
Ad
sorp
tio
n [
μg
/m2]
SSW
5 w t% NaCl
HPAM
Dynamic retention: Effect of molecular weightSulfonation degree = 25%
T = 20C
0
20
40
60
80
100
120
140
0 4 8 12 16
Molecular weight [MDa]
Ad
sorp
tio
n [
μg
/g]
SSW
5 w t% NaClHPAM
Practical applications Both retention and viscosity are important for practical use of
polymers
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35
Sulfonation degree (mole %)
Ret
enti
on
(µ
g/g
)
0
5
10
15
20
25
30
35
Vis
cosi
ty (
mP
a.se
c)
Retention 5wt% NaCl
Viscosity 5wt% NaCl
Conclusions
• Sulfonated polyacrylamide polymers have considerably lower levels of both adsorption and retention than corresponding carboxylates
• Increasing the sulfonation degree reduces levels of both static adsorption and dynamic retention
• Static adsorption show an increasing trend with respect to increasing molecular weight
• Dynamic retention, however, show a decreasing trend with respect to increasing molecular weight
Conclusions
• At equal ionic strengths the presence of divalent cations leads to increased adsorption and retention
• Viscosity is maintained even at high sulfonation degree,but there is a substantial decrease in adsorption and retention
• This combination of factors makes samples with a high degree of sulfonation especially interesting for polymer flooding in high salinity reservoirs.