1. Salt Tolerant Synthetic Polymers Effects on adsorption and retention
Masoud Rashidi
Sigmund Sandvik
Anne Marit Blokhus
Arne Skauge
Presented by Ketil Djurhuus
IEA Collaborative Project on EOR 30th Annual Workshop and Symposium September, Canberra, Australia

2. Outline Introduction and motivation Materials and experiments
Static and dynamic retention
Practical applications
Conclusions

3. Why polymer flooding? High mobility ratio Low mobility ratio
Improve area sweep
Reduce viscous fingering
Before polymer flooding After polymer flooding
High mobility ratio Low mobility ratio

4. Limitations of conventional polymers
Salinity (wt.%) 10 5 20 50
100
150
Temperature (°C)
Xanthan
HPAM

5. 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.

6. Materials HPAM little salt tolerant Sulfonated copolymers
have improved
solution properties
Sulfonation improves salt
tolerance compared to
carboxylates
Sulfonated polymers are
less prone to precipitation
Hydrolyzed polyacrylamide
Sulfonated polyacrylamide

7. Sulfonation degree (mole %) 1 Molecular weight = 6 MDalton
Experimental plan
Varying sulfonation degree
Molecular weight = 8 MDalton
Polymers
HPAM
AN 105
AN 113
AN125
AN 132
Sulfonation degree (mole %) 51 13 25 32
1 Molecular weight = 6 MDalton
Varying molecular weight
Sulfonation degree = 25 mole%
Polymers
AN 125
VLM
AN125
VHM Mw
(MDalton) 2 8 12

8. 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

9. Static adsorption
Adsorption isotherm on kaolinite. SD= 13% Mw = 8 MDalton
S/L= 0.005, T = 20C, Salinity = 5 wt% NaCl

10. Static adsorption: Effect of sulfonation
Mw = 8 MDalton
S/L= 0.005, T = 20C

11. Static adsorption: Effect of molecular weight
Sulfonation degree = 25%
S/L= 0.005, T = 20C

12. Dynamic retention
Dynamic retention profile on a Berea core. SD= 25% Mw = 12 MDalton. T = 20C. Salinity = SSW

13. Dynamic retention: Effect of sulfonation
Mw = 8 MDalton
T = 20C

14. Dynamic retention: Effect of molecular weight
Sulfonation degree = 25%
T = 20C

15. Practical applications
Both retention and viscosity are important for practical use of polymers

16. 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

17. 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.