Synthetic polymers for Enhanced Oil Recovery; Mechanical degradation, and alleviation thereof: Experimental study across scales in pipes, chokes, and porous media of regular HPAM, HPAM-ATBS co-polymers, and TAPs


Siv Marie Åsen
Keywords: synthetic polymers, enhanced oil recovery, eor


This thesis and the related work concern synthetic polymers for enhanced oil recovery, their ability to reduce the mobility of the water phase during oil recovery, and their predisposition to mechanically break when subjected to certain flow conditions.

A major problem during water injection for pressure support and to push oil through the reservoir, is the adverse mobility ratio between water and oil. Water will usually have a lower viscosity than the oil, meaning it has less resistance to flow and moves more easily. It also flows more easily where the water saturation is high, giving a self-enforcing nature to viscous instabilities. In short, water will create low resistance flow paths for itself or flow in paths of low resistance, reaching the producer at a relatively early stage of injection and with large volumes of oil remaining to be produced. If the mobility difference between the injected phase and the oil is reduced, the oil will be displaced in a more piston-like manner, accelerating the oil production, increasing the volume of the reservoir contacted by the water, and delaying the water production.

The mobility difference can be improved by decreasing the mobility of the water phase through making it more viscous. This can be done by adding polymers. Polymer are large molecules composed of repeating chemical building blocks. The polymers used for Enhanced oil recovery (EOR) have molecular weight of millions of g/mol, so large that only a few hundred ppms added to the water is needed to increase the viscosity significantly.

Three categories of synthetic water-soluble polymers have been studied in this work, partly hydrolyzed polyacrylamide (HPAM), HPAM-ATBS co-polymers, and thermo-thickening associative polymers (TAPs). Their flow behaviour has been studied across scales in tubes, chokes, and porous media (unconsolidated sand, and Berea and Bentheimer sandstone).

HPAM is worldwide the most used polymer for Enhanced Oil Recovery (EOR), but there are several issues related to its use:

  • Viscosity is reduced in saline water
  • It thickens in porous media at high flow rates typical for the injection zone, resulting in pressure build-up, poor injectivity or the creation of fractures
  • It is prone to mechanical degradation at harsh flow conditions, an effect amplified in saline water

Mechanical degradation is that the backbone of the polymer molecules ruptures, resulting in a polymer with a lower molecular weight and correspondingly lower viscosity, making the solution less effective in pushing oil to the producer.

HPAM-ATBS co-polymers are derivatives of HPAM that have been modified to be less influenced by salt in the mixing water. Due to a, on the molecular level, large appendix on the ATBS segments in the polymer, the polymer solutions’ viscosity is not influenced as much by salt as HPAM. This is because it, due to steric hindrance, remains expanded. Also, since it remains expanded, mechanical degradation will not increase with salinity of the mixing water.

TAPs are polymers mainly composed of HPAM and (H)PAM-ATBS (or other water-soluble polymers), that have been modified to be triggered by heat. At a certain temperature, segments of them will become hydrophobic and through hydrophobic interactions, they bind weakly to each other creating a reversible weakly cross-linked gel with increased resistance to flow. This effect is, in addition to being triggered by heat, also enhanced by salt and porous media flow, and is strongly shear-thinning. This makes TAPs very promising for EOR operations as they will have low resistance to flow at the high injection rates at the often cooled down injection zone, and high resistance to flow at the low rates of the warmer main part of the reservoir. As their thickening does not only rely on the molecular weight, lower molecular weight polymers can be used. Lower molecular weight polymers are less predisposed to mechanical degradation and injectivity problems.

Degradation experiments in cylindrical pipes of different dimensions also confirmed that salt accelerates mechanical degradation more for HPAM than for HPAM-ATBS, and that high molecular weight polymers are more prone to mechanical degradation than low molecular weight. It was also found that mechanical degradation scales with shear rate, and not with pressure drop, velocity or Reynolds number, and that even at turbulent flow, degradation will not increase with length of the tube. That is, degradation seems to be limited to the inlet of the flow constriction. Since pressure drop itself does not harm the polymer, polymer solutions can be choked (have its pressure reduced) as long at the shear rate is kept below a critical value. Three methods for choking with acceptable degradation were experimentally identified: 1) Take the pressure drop out over a longer distance (long tube), 2) Use several chokes in series, each below a critical pressure drop or 3) Choke concentrated solution.

Testing of TAPs with increasing content of the temperature-triggered segment in different porous media confirmed the assumption that a critical concentration of either polymer or the active segments are needed to achieve thermo- thickening. It was also confirmed that below their critical temperature, their flow behaviour is like the unmodified mother polymer, and this is also (for the most part) the case for bulk flow (tube flow), even at elevated temperature. These experiments were not performed to study mechanical degradation and were run below the critical shear rate for degradation, but their high flow rate behaviour will most likely be that of a medium molecular weight PAM-ATBS co-polymer, as that is the main constituent of these polymers. The experiments revealed that within the limited diversity of these tests, type of porous media did not significantly influence the thermo-thickening. At high salinity, homogenous and stable thermo-thickening was achieved in a 76 cm long sand- pack, but the build-up of resistance to flow was slow, and for the weaker systems tested (lower associative content or salinity), resistance to flow collapsed at very low velocities. These systems still show great  promise regarding EOR, but a better understanding of the mechanisms guiding their behaviour is needed for optimum design for specific field conditions.

Author Biography

Siv Marie Åsen

PhD Candidate
University of Stavanger
Faculty of Science and Technology, Department of Energy Resources


Amit, D. J., Parisi, G., & Peliti, L. (1983). Asymptotic behavior of the" true" self-avoiding walk. Physical Review B, 27(3), 1635.

Askarinezhad, R., Universitetet i Stavanger Institutt for energi- og, p., & Universitetet i, S. (2018). Produced water management : chemical water shutoff and disproportionate permeability reduction University of Stavanger, Faculty of Science and Technology, Department of Petroleum Engineering]. Stavanger.

Austad, T., Strand, S., Madland, M. V., Puntervold, T., & Korsnes, R. I. (2007). Seawater in chalk: an EOR and compaction fluid. International petroleum technology conference,

Azad, M. S., & Trivedi, J. J. (2019). Quantification of the viscoelastic effects during polymer flooding: a critical review. SPE Journal, 24(06), 2,731- 732,757.

Azad, M. S., & Trivedi, J. J. (2020). Extensional Effects during Viscoelastic Polymer Flooding: Understanding Unresolved Challenges. SPE Journal.

Baschnagel, J., Wittmer, J. P., & Meyer, H. (2004). Monte Carlo simulation of polymers: coarse-grained models. arXiv preprint cond-mat/0407717.

Baviere, M. (1991). Basic concepts in enhanced oil recovery processes.

Blasius, H. (1913). Das aehnlichkeitsgesetz bei reibungsvorgängen in flüssigkeiten. In Mitteilungen über Forschungsarbeiten auf dem Gebiete des Ingenieurwesens (pp. 1-41). Springer.

Bokias, G., Hourdet, D., & Iliopoulos, I. (2000). Positively charged amphiphilic polymers based on poly (N-isopropylacrylamide): Phase behavior and shear-induced thickening in aqueous solution. Macromolecules, 33(8), 2929-2935.

Borling, D., Chan, K., Hughes, T., & Sydnask, R. (1994). Pushing out the oil with conformance control. Oilfield Review;(Netherlands), 6(2).

Cannella, W., Huh, C., & Seright, R. (1988). Prediction of xanthan rheology in porous media. SPE annual technical conference and exhibition,

Carman, P. C. (1956). Flow of gases through porous media.

Cohen, Y., & Christ, F. (1986). Polymer retention and adsorption in the flow of polymer solutions through porous media. SPE Reservoir Engineering, 1(02), 113-118.

Culter, J. D., Zakin, J. L., & Patterson, G. K. (1975). Mechanical degradation of dilute solutions of high polymers in capillary tube flow. Journal of Applied Polymer Science, 19(12), 3235-3240.

Du, H., Wickramasinghe, R., & Qian, X. (2010). Effects of salt on the lower critical solution temperature of poly (N-isopropylacrylamide). The Journal of Physical Chemistry B, 114(49), 16594-16604.

Dupuis, G., Rousseau, D., Tabary, R., & Grassl, B. (2011). Flow of hydrophobically modified water-soluble-polymer solutions in porous media: New experimental insights in the diluted regime. SPE Journal, 16(01), 43-54.

Durand, A., & Hourdet, D. (1999). Synthesis and thermoassociative properties in aqueous solution of graft copolymers containing poly (N- isopropylacrylamide) side chains. Polymer, 40(17), 4941-4951.

Durand, A., & Hourdet, D. (2000). Thermoassociative graft copolymers based on poly (N‐isopropylacrylamide): Relation between the chemical structure and the rheological properties. Macromolecular Chemistry and Physics, 201(8), 858-868.<858::AID-MACP858>3.0.CO;2-6

Emadi, A. (2012). Enhanced heavy oil recovery by water and carbon dioxide flood Heriot-Watt University Edinburgh, UK].

Fathi, S. J., Austad, T., & Strand, S. (2012). Water-Based Enhanced Oil Recovery EOR by Smart Water in Carbonate Reservoirs. SPE EOR conference at oil and gas West Asia,

Fjelde, I., Asen, S. M., & Omekeh, A. V. (2012). Low salinity water flooding experiments and interpretation by simulations. SPE improved oil recovery symposium,

Fjelde, I., Omekeh, A. V., & Sokama-Neuyam, Y. A. (2014). Low salinity water flooding: Effect of crude oil composition. SPE Improved Oil Recovery Symposium,

Freed, K. F. (1981). Polymers as self-avoiding walks. The Annals of Probability, 537-554.

Gathier, F., Christophe, R., Lionel, L., & Antoine, T. (2020). Offshore Polymer EOR Injection Philosophies, Constrains and Solutions. SPE Improved Oil Recovery Conference,

Han, M., Xiang, W., Zhang, J., Jiang, W., & Sun, F. (2006). Application of EOR technology by means of polymer flooding in Bohai Oilfields. International Oil & Gas Conference and Exhibition in China,

Hirasaki, G., & Pope, G. (1974). Analysis of factors influencing mobility and adsorption in the flow of polymer solution through porous media. Society of Petroleum Engineers Journal, 14(04), 337-346.

Hourdet, D., L'alloret, F., & Audebert, R. (1994). Reversible thermothickening of aqueous polymer solutions. Polymer, 35(12), 2624-2630.

Israelachvili, J. N. (2011). Intermolecular and surface forces. Academic press. Jensen, T., Harpole, K., & Østhus, A. (2000). EOR screening for Ekofisk. SPE European Petroleum Conference,

Jolma, I., Strand, D., Stavland, A., Fjelde, I., & Hatzignatiou, D. (2017). When size matters-polymer injectivity in chalk matrix. IOR 2017-19th European Symposium on Improved Oil Recovery,

Jouenne, S., Anfray, J., Levitt, D., Souilem, I., Marchal, P., Lemaitre, C., Choplin, L., Nesvik, J., & Waldman, T. (2015). Degradation (or lack thereof) and drag reduction of HPAM solutions during transport in turbulent flow in pipelines. Oil and gas facilities, 4(01), 80-92.

Jouenne, S., Chakibi, H., & Levitt, D. (2018). Polymer stability after successive mechanical-degradation events. SPE Journal, 23(01), 18-33.

Kamal, M. S., Sultan, A. S., Al-Mubaiyedh, U. A., & Hussein, I. A. (2015). Review on polymer flooding: rheology, adsorption, stability, and field applications of various polymer systems. Polymer Reviews, 55(3), 491- 530.

Karami, H. R., Rahimi, M., & Ovaysi, S. (2018). Degradation of drag reducing polymers in aqueous solutions. Korean Journal of Chemical Engineering, 35(1), 34-43.

Kim, C., Kim, J., Lee, K., Choi, H., & Jhon, M. (2000). Mechanical degradation of dilute polymer solutions under turbulent flow. Polymer, 41(21), 7611-7615.

Kim, U., & Carty, W. M. (2016). Effect of polymer molecular weight on adsorption and suspension rheology. Journal of the Ceramic Society of Japan, 124(4), 484-488.

Kozeny, J. (1927). Uber kapillare leitung der wasser in boden. Royal Academy of Science, Vienna, Proc. Class I, 136, 271-306.

Kronberg, B., Holmberg, K., & Lindman, B. (2014). Surface chemistry of surfactants and polymers. John Wiley & Sons.

Kruschwitz, S., Halisch, M., Prinz, C., Weller, A., Müller-Petke, M., & Dlugosch, R. (2017). Towards a better understanding of electrical relaxation. Annual Symposium of the Society of Core Analysts (SCA) Proceedings,

Kwak, H. T., Zhang, G., & Chen, S. (2005). The effects of salt type and salinity on formation water viscosity and NMR responses. proceedings of the international symposium of the Society of Core Analysts, Toronto, Canada,

L'alloret, F., Maroy, P., Hourdet, D., & Audebert, R. (1997). Reversible thermoassociation of water-soluble polymers. Revue de l'Institut Français du Pétrole, 52(2), 117-128.

Langaas, K., & Stavland, A. (2020). Water Shutoff with Polymer in the Alvheim Field. SPE Production & Operations, 35(02), 335-350.

Lara-Ceniceros, T. E., Cadenas-Pliego, G., Rivera-Vallejo, C. C., de León- Gómez, R. E. D., Coronado, A., & Jiménez-Regalado, E. J. (2014). Synthesis and characterization of thermo-insensitive, water-soluble associative polymers with good thickening properties at low and high temperatures. Journal of Polymer Research, 21(7), 1-12.

Leblanc, T., Braun, O., Thomas, A., Divers, T., Gaillard, N., & Favero, C. (2015). Rheological properties of stimuli-responsive polymers in solution to improve the salinity and temperature performances of polymer-based chemical enhanced oil recovery technologies. SPE Asia Pacific Enhanced Oil Recovery Conference,

Lohne, A., Nødland, O., Stavland, A., & Hiorth, A. (2017). A model for non- Newtonian flow in porous media at different flow regimes. Computational Geosciences, 21(5), 1289-1312.

Maerker, J. M. (1975). Shear degradation of partially hydrolyzed polyacrylamide solutions. Society of Petroleum Engineers Journal, 15(04), 311-322.

Maloney, D., Honarpour, M., & Brinkmeyer, A. (1990). The effects of rock characteristics on relative permeability.

Manrique, E., Ahmadi, M., & Samani, S. (2017). Historical and recent observations in polymer floods: an update review. CT&F Ciencia, Tecnología y Futuro, 6(5), 17-47.

Martin, F. (1986). Mechanical degradation of polyacrylamide solutions in core plugs from several carbonate reservoirs. SPE Formation Evaluation, 1(02), 139-150.

Muggeridge, A., Cockin, A., Webb, K., Frampton, H., Collins, I., Moulds, T., & Salino, P. (2014). Recovery rates, enhanced oil recovery and technological limits. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372(2006), 20120320.

NorwegianPetroleum. (2019). The government's revenues. URL:

Nouri, H. H., & Root, P. J. (1971). A study of polymer solution rheology, flow behavior, and oil displacement processes. Fall Meeting of the Society of Petroleum Engineers of AIME,

NPD. (2019). NPD. Retrieved 31.01.2021 from

Nødland, O., Lohne, A., Stavland, A., & Hiorth, A. (2019). An investigation of polymer mechanical degradation in radial well geometry. Transport in Porous Media, 128(1), 1-27.

Nødland, O. M. (2019). Core scale modelling of EOR transport mechanisms University of Stavanger, Faculty of Science and Technology, Department of Mathematics and Natural Sciences]. Stavanger, Norway.

Palmer, T. L., Baardsen, G., & Skartlien, R. (2018). Reduction of the effective shear viscosity in polymer solutions due to crossflow migration in microchannels: Effective viscosity models based on DPD simulations. Journal of Dispersion Science and Technology, 39(2), 190-206.

Piñerez T, I. D., Austad, T., Strand, S., Puntervold, T., Wrobel, S., & Hamon, G. (2016). Linking low salinity EOR effects in sandstone to pH, mineral properties and water composition. SPE Improved Oil Recovery Conference,

Polymer Properties Database (2015-2016).,broader%20the%20molecular%20weight%20distribution.&text=where%20%5B%CE%B7%5D%20is%20the%20intrinsic,been%20measured%20for%20many%20polymers

Poole, R. (2012). The deborah and weissenberg numbers. Rheol. Bull, 53(2), 32-39.

Pye, D. J. (1964). Improved secondary recovery by control of water mobility. Journal of Petroleum technology, 16(08), 911-916.

Reichenbach-Klinke, R., Stavland, A., Langlotz, B., Wenzke, B., & Brodt, G. (2013). New insights into the mechanism of mobility reduction by associative type copolymers. SPE Enhanced Oil Recovery Conference, Reichenbach-Klinke, R., Stavland, A., Strand, D., Langlotz, B., & Brodt, G. (2016). Can associative polymers reduce the residual oil saturation? SPE EOR Conference at Oil and Gas West Asia,

Reichenbach-Klinke, R., Zimmermann, T., Stavland, A., & Strand, D. (2018). Temperature-Switchable Polymers for Improved Oil Recovery. SPE Norway One Day Seminar,

Reiner, M. (1964). The deborah number. Physics today, 17(1), 62.

Ritchie, H. (2020). Energy mix. Retrieved 12.01.2021 from

Ruiz-Cañas, M.-C., Quintero-Perez, H.-I., Castro-Garcia, R.-H., & Romero- Bohorquez, A. R. (2020). USE OF NANOPARTICLES TO IMPROVE THERMOCHEMICAL RESISTANCE OF SYNTHETIC POLYMER TO ENHANCED OIL RECOVERY APPLICATIONS: A REVIEW. CT&F-Ciencia, Tecnología y Futuro, 10(2), 85-97.

Ryles, R. (1988). Chemical stability limits of water-soluble polymers used in oil recovery processes. SPE Reservoir Engineering, 3(01), 23-34.

Sachdeva, J. S., Nermoen, A., Korsnes, R. I., & Madland, M. V. (2020). Effect of Initial Wettability on Rock Mechanics and Oil Recovery: Comparative Study on Outcrop Chalks. Transport in Porous Media, 133(1), 85-117.

Seright, R., & Skjevrak, I. (2015). Effect of dissolved iron and oxygen on stability of hydrolyzed polyacrylamide polymers. SPE Journal, 20(03), 433-441.

Seright, R. S. (1983). The effects of mechanical degradation and viscoelastic behavior on injectivity of polyacrylamide solutions. Society of Petroleum Engineers Journal, 23(03), 475-485.

Seright, R. S., Fan, T., Wavrik, K., & de Carvalho Balaban, R. (2011). New insights into polymer rheology in porous media. SPE Journal, 16(01), 35-42.

Sheng, J. J., Leonhardt, B., & Azri, N. (2015). Status of polymer-flooding technology. Journal of Canadian petroleum technology, 54(02), 116- 126.

Skrettingland, K., Dale, E. I., Stenerud, V. R., Lambertsen, A. M., Nordaas Kulkarni, K., Fevang, O., & Stavland, A. (2014). Snorre In-depth Water Diversion Using Sodium Silicate-Large Scale Interwell Field Pilot. SPE EOR Conference at Oil and Gas West Asia,

Skrettingland, K., Holt, T., Tweheyo, M. T., & Skjevrak, I. (2011). Snorre low- salinity-water injection-coreflooding experiments and single-well field pilot. SPE Reservoir Evaluation & Engineering, 14(02), 182-192.

Smalley, P., Muggeridge, A., Dalland, M., Helvig, O., Høgnesen, E., Hetland, M., & Østhus, A. (2018). Screening for EOR and Estimating Potential Incremental Oil Recovery on the Norwegian Continental Shelf. SPE Improved Oil Recovery Conference,

Sorbie, K. (1991). Polymer-improved oil recovery.

Standnes, D. C., & Skjevrak, I. (2014). Literature review of implemented polymer field projects. Journal of Petroleum Science and Engineering, 122, 761-775.

Stavland, A., Jonsbraten, H., Lohne, A., Moen, A., & Giske, N. H. (2010). Polymer flooding-flow properties in porous media versus rheological parameters. SPE EUROPEC/EAGE Annual Conference and Exhibition,

Stavland, A., & Nilsson, S. (2001). Segregated flow is the governing mechanism of disproportionate permeability reduction in water and gas shutoff. SPE annual technical conference and exhibition,

Stavland, A., Åsen, S. M., Mebratu, A., & Gathier, F. (2021). Scaling of Mechanical Degradation of EOR Polymers: From Field-Scale Chokes to Capillary Tubes. SPE Production & Operations, 36(01), 43-56.

Szabo, M. T. (1975). Some aspects of polymer retention in porous media using a C14-tagged hydrolyzed polyacrylamide. Society of Petroleum Engineers Journal, 15(04), 323-337.

Taylor, K. C., & Nasr-El-Din, H. A. (1998). Water-soluble hydrophobically associating polymers for improved oil recovery: A literature review. Journal of Petroleum Science and Engineering, 19(3-4), 265-280.

Teeuw, D., & Hesselink, F. T. (1980). Power-law flow and hydrodynamic behaviour of biopolymer solutions in porous media. SPE Oilfield and Geothermal Chemistry Symposium,

Warner, H. (1976). Analysis of mechanical degradation data on partially hydrolyzed polyacrylamide solutions. SPE J.

Weast, R. C., & Astle, M. (1983). CRC Handbook of Chemistry and Physics (63 ed.).

Zaitoun, A., & Kohler, N. (1987). The role of adsorption in polymer propagation through reservoir rocks. SPE International Symposium on Oilfield Chemistry,

Zaitoun, A., Makakou, P., Blin, N., Al-Maamari, R. S., Al-Hashmi, A., Abdel- Goad, M., & Al-Sharji, H. H. (2012). Shear stability of EOR polymers. SPE Journal, 17(02), 335-339.

Zhang, G., & Seright, R. (2014). Effect of concentration on HPAM retention in porous media. SPE Journal, 19(03), 373-380.

Zheng, C., Gall, B., Gao, H., Miller, A., & Bryant, R. (2000). Effects of polymer adsorption and flow behavior on two-phase flow in porous media. SPE Reservoir Evaluation & Engineering, 3(03), 216-223.

Zhong, C., Luo, P., Ye, Z., & Chen, H. (2009). Characterization and solution properties of a novel water-soluble terpolymer for enhanced oil recovery. Polymer Bulletin, 62(1), 79-89.

Zhu, Y., Xu, Y., & Huang, G. (2013). Synthesis and aqueous solution properties of novel thermosensitive polyacrylamide derivatives. Journal of Applied Polymer Science, 130(2), 766-775.

Åm, K., Al-Kasim, F., Bjerkedal, N., Gjerdseth, A., Kindem, S., Skauge, A., Skjaerpe, T., Sund, B., Saetre, J., & Wiborg, R. (2010). Oekt utvinning paa norsk kontinentalsokkel-en rapport fra utvinningsutvalget. Olje-og energidepartementet, Oslo.

Åsen, S. M., Stavland, A., & Strand, D. (2021). Flow behavior of thermo- thickening associative polymers in porous media: Effects of associative content, salinity, time, velocity, and temperature. Submitted to Transport in Porous Media.

Åsen, S. M., Stavland, A., Strand, D., & Hiorth, A. (2018). An experimental investigation of polymer mechanical degradation at cm and m scale. SPE Improved Oil Recovery Conference,

Åsen, S. M., Stavland, A., Strand, D., & Hiorth, A. (2019). An Experimental Investigation of Polymer Mechanical Degradation at the Centimeter and Meter Scale. SPE Journal, 24(04), 1,700-701,713.

Cover for Synthetic polymers for Enhanced Oil Recovery; Mechanical degradation, and alleviation thereof: Experimental study across scales in pipes, chokes, and porous media of regular HPAM, HPAM-ATBS co-polymers, and TAPs
June 17, 2021