INVESTIGATION OF BRINE PH EFFECT ON THE RHEOLOGICAL AND VISCOELASTIC PROPERTIES OF HPAM POLYMER FOR AN OPTIMIZED ENHANCED OIL RECOVERY DESIGN
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Date
2022
Authors
Shakeel, Mariam
Pourafshary, Peyman
Hashmet, Muhammad Rehan
Journal Title
Journal ISSN
Volume Title
Publisher
ACS Omega
Abstract
A novel approach to improve viscous and viscoelastic
properties by exploiting the pH and salinity sensitivity of HPAM
polymer is proposed in this paper. Polymer flooding is a welldeveloped
and effective enhanced oil recovery technique. The design
of the makeup brine is one of the most critical phases of a polymer
flood project, since the brine composition, salinity, and pH directly
influence the polymer viscosity and viscoelasticity. However, the
viscoelastic properties of hydrolyzed polyacrylamide polymers have
not been given much consideration during the design phase of
polymer flood projects. Our experimental study focuses on the
optimization of the makeup water design for polymer flooding by
evaluating the optimum solution salinity and pH for better stability
and improved viscoelastic behavior of the polymer. Initially, the brine
salinity and ionic composition is adjusted and then hydrolyzed polyacrylamide (HPAM) polymer solutions of varying pH are
prepared using the adjusted brine. Rheological experiments are conducted over a temperature range of 25−80 °C and at different
aging times. Polymer thermal degradation as a function of pH is assessed by examining the solutions at 80 °C for 1 week. Amplitude
sweep and frequency sweep tests are performed to determine the viscoelastic properties such as storage modulus, loss modulus, and
relaxation time. A 15−40% increase in the polymer solution viscosity and a 20 times increase in relaxation time is observed in the pH
range of 8−10 in comparison to the neutral solution. This can be attributed to the low-salinity ion-adjusted environment of the
makeup brine and further hydrolysis and increased repulsion of polymer chains in an alkaline environment. These results indicate
that the viscoelastic properties of a polymer are tunable and a basic pH is favorable for better synergy between the brine and the
polymer. Alkaline low-salinity polymer solutions have exhibited 60% higher thermal stability in comparison to acidic solutions and
thus can be successfully applied in high-temperature reservoirs. The results of this study show that polymer solutions with an
optimum pH in the basic range exhibit a higher viscoelastic character and an increased resistance toward thermal degradation.
Hence, the polymer solution salinity, ionic composition, and pH should be adjusted to obtain maximum oil recovery by the polymer
flooding method. Finally, this study shows that more effective polymer solutions can be prepared by adjusting the pH and designing
a low-salinity water/polymer recipe to get the additional benefit of polymer viscoelasticity. The optimized low-salinity alkaline
conditions can reduce the residual oil saturation by stronger viscous and viscoelastic forces developed by more viscous polymers.
The findings of this study can be employed to design an optimum polymer recipe by tuning the brine pH and salinity for maximum
incremental oil recovery, particularly in high-temperature and high-salinity formations.
Description
Keywords
Type of access: Open Access, HPAM Polymer, Polymer chains, Polymer solutions, Polymers
Citation
Shakeel, M., Pourafshary, P., & Hashmet, M. R. (2022). Investigation of Brine pH Effect on the Rheological and Viscoelastic Properties of HPAM Polymer for an Optimized Enhanced Oil Recovery Design. ACS Omega, 7(17), 14961–14971. https://doi.org/10.1021/acsomega.2c00699