6. Conclusions


rigidity. However, due to losses of frictional heat in the form of thermal energy, a decrease of

Increasing the ionic strength (brine 8.4 wt%) and temperature significantly affects the structural strength of polymer AP1 and the SAP-AP1 system (see Figure 11). Similarly, the downward curve (i.e. cooling process) shows a decreasing structural strength relative to the corresponding heating curves. The SAP-AP1 temperature curve shows a higher structural

there is no difference between the AP1 polymer and the SAP-AP1 system. Furthermore, the tanδ-curve of the cooling process for the SAP-AP1 system shows a shift from tanδ-values > 1 at elevated temperatures to tanδ-values < 1 at lower temperatures. This makes evident that at elevated temperatures, the SAP-AP1 network system changes its flow behavior, showing

more rigid and the tanδ-values become < 1, showing again the consistency of a rigid supramo-

At elevated ionic strength (i.e. 8.4 wt% brine), the baseline polymers AP2 and AP3 and their corresponding SAP-AP systems show similar behavior to the baseline AP1 and SAP-AP1, discussed above. Nevertheless, it is important to mention that the SAP-AP2 system shows the highest structural strength in terms of G<sup>0</sup> and G<sup>00</sup> and the least hysteresis between the heating and the cooling curves among the systems. These observations make evident that the optimum SAP-AP2 displays enhanced structural strength at elevated temperatures and ionic strengths

The AP and SAP-AP systems were subjected to a thermal stability test at 90�C for a period of 8 weeks. The presence of dissolved oxygen at high temperatures might induce the formation of free radicals which degrade the polymer molecule by cleavage reducing its molecular weight and viscosifying functionality [2]. Besides, if dissolved oxygen is present in the polymer solutions together with very low concentrations of dissolved iron, it might also cause substantial polymer degradation [4, 26–30]. Therefore, to prevent chemical degradation, the AP and the SAP-AP samples were placed in a glove chamber and bubbled with nitrogen at a pressure ranging from 10 to 20 psi for a period of 30 min. Two duplicated set of samples of the AP and the SAP-AP systems were prepared in two different brine salinity concentrations: 2.1 and 8.4 wt% and placed in the oven at 90 � 0.5�C for 8 weeks. Every 2 weeks, a set of samples were taken out of the oven and subjected to rheological analysis. Figure 13 displays the G<sup>0</sup>

G00-curves as a function of angular frequency and time for the AP and SAP-AP systems at brine

In low-salinity brine, samples AP1, AP2, SAP-AP1, and SAP-AP2 show precipitation of solids and color change at week # 4; while in samples AP3 and SAP-AP3, the precipitation of solids was observed at week # 8. In high-salinity brine, precipitation of solids took place faster at week # 2.

G<sup>0</sup> and G<sup>00</sup> is observed for all the samples in both low and high salinities.


, performing as a viscoelastic liquid. As temperature decreases, the network becomes


the G00-values is observed in the cooling temperature curve" [22].

strength in terms of G<sup>0</sup>

218 Cyclodextrin - A Versatile Ingredient

G<sup>00</sup> > G<sup>0</sup>

The G<sup>0</sup>

lecular structure.

compared to the baseline.

5.2. Long-term thermal stability

salinity concentrations of 2.1 and 8.4 wt%.

In summary, we formulated advanced polymer-surfactant systems via self-assembling driven by host-guest chemistry and other physical noncovalent bonding by mixing associating polymers, with an anionic surfactant, and β-CD in brine solutions. The optimum supramolecular systems were subjected to rheological characterization and several stability testing techniques to establish their tolerance to increasing ionic strength concentration, shear degradation, and thermal stability. The most significant findings are outlined as follows:

Author details

New Brunswick, Canada

References

pp. 1-11

2095

Laura Romero-Zerón\* and Xingzhi Jiang

\*Address all correspondence to: laurarz@unb.ca

Chemical Engineering Department, University of New Brunswick, Fredericton,

13-171); Jun 30–Jul 5, 2013. Anchorage, Alaska: 2013. pp. 81-85

Gas Show; September 25–28, 2011; Manama, Bahrain: 2011. pp. 1-9

dian Petroleum Technology. 2015;54(02):16-26

Rapid Communications. 2014;35(13):1166-1184

Reviews. 2014;43(20):6881-6893

stability of EOR polymers. SPE Journal. 2012;17(02):335-339

[1] Kang PS, Lim JS, Huh C. A novel approach in estimating shear-thinning rheology of HPAM and AMPS polymers for enhanced oil recovery using artificial neural network. In: The Twenty-third International Offshore and Polar Engineering Conference (ISOPE-I-

Advanced Polymer-Surfactant Systems via Self-Assembling

http://dx.doi.org/10.5772/intechopen.74618

221

[2] Vermolen E, Van Haasterecht MJ, Masalmeh SK, Faber MJ, Boersma DM, Gruenenfelder MA. Pushing the envelope for polymer flooding towards high-temperature and highsalinity reservoirs with polyacrylamide based ter-polymers. In: SPE Middle East Oil and

[3] Wu Y, Mahmoudkhani A, Watson P, Fenderson TR, Nair M. Development of new polymers with better performance under conditions of high temperature and high salinity. In: SPE EOR Conference at Oil and Gas West Asia; April 16–18, 2012; Muscat, Oman: 2012.

[4] Sheng JJ, Leonhardt B, Azri N. Status of polymer-flooding technology. Journal of Cana-

[5] Zaitoun A, Makakou P, Blin N, Al-Maamari RS, Al-Hashmi AA, Abdel-Goad M. Shear

[6] Levitt D, Pope GA. Selection and screening of polymers for enhanced-oil recovery. In: SPE Symposium on Improved Oil Recovery; April 19–23, 2008; Tulsa, Oklahoma: pp. 1-18 [7] Tan S, Ladewig K, Fu Q, Blencowe A, Qiao GG. Cyclodextrin-based supramolecular assemblies and hydrogels: Recent advances and future perspectives. Macromolecular

[8] Hu J, Liu S. Engineering responsive polymer building blocks with host–guest molecular recognition for functional applications. Accounts of Chemical Research. 2014;47(07):2084-

[9] Adler-Abramovich L, Gazit E. The physical properties of supramolecular peptide assemblies: From building block association to technological applications. Chemical Society

