Can copolymerization kinetics help tailor properties of poly (acrylamide/acrylic acid) for enhanced oil recovery?
May 10-15, 2015
Among water-soluble polymers, copolymers of acrylamide (AAm) and acrylic acid (AAc) are probably the most common and widely used. One important application of AAm/AAc copolymers with growing interest in both fundamental and applied areas is in enhanced oil recovery (EOR). One of the drawbacks of AAm/AAc copolymers in EOR is the lack of stability in viscous and viscoelastic properties when copolymers are subjected to combined effects of temperature, shear and elongational stresses. The result of such effects is a decline in performance properties and efficiency in EOR. Since application properties are tied to both the microstructure and macrostructure of the copolymer, which are in turn related to the underlying kinetics of the copolymerization, systematic kinetic studies provide a better understanding of possible influential factors in copolymerizations and copolymer properties. However, information on the kinetics of the AAm/AAc radical copolymerization is rather scarce. It is also clear, after reviewing the literature, that the dependency of AAm/AAc kinetics on pH and ionic strength (due to the electrolyte nature of the monomers) makes the system even more complicated. The focus of this research was first to clarify comonomer reactivity ratios, which were very inconsistent in the literature, and to proceed with an optimal approach to estimate reliable reactivity ratio values. Secondly, a systematic study was conducted on AAm/AAc copolymerization kinetics to investigate the effects of various factors such as pH, ionic strength and monomer concentration, on different responses (such as monomer reactivity ratios, monomer conversion, copolymer composition, monomer sequence length, and copolymer molecular weight) in order to understand the copolymerization kinetics thoroughly. For example, the effect of ionic strength on the reactivity ratios is shown in Figure 1. Figure 1- Reactivity ratio point estimates and joint confidence regions for different Ionic Strength (IS) levels in AAm/AAc copolymerization. After clarifying the kinetics, one can manipulate microstructure chain properties such as molecular weight and copolymer composition, which in turn enable the control of macrostructure bulk properties of the copolymer. Therefore, in the third step, copolymer properties such as solution viscosity and viscoelastic properties (such as elastic and viscous modulus) were evaluated in order to correlate copolymer microstructure to macrostructure (meaningful structure-property relationships). In the fourth and last step, we are in the process of testing copolymer performance in EOR. To do so, polymer flooding and oil displacement tests are being applied on copolymers with carefully selected chain properties in order to tailor and fine-tune AAm/AAc copolymers for achieving higher oil recovery efficiency.
Marzieh Riahinezhad, Neil McManus, and Alexander Pendilis, "Can copolymerization kinetics help tailor properties of poly (acrylamide/acrylic acid) for enhanced oil recovery?" in "Polymer Reaction Engineering IX", E. Vivaldo-Lima, UNAM; J. Debling, BASF; F. Zaldo-Garcia, CP-COMEX; J. Tsavalas, Univ. of New Hampshire Eds, ECI Symposium Series, (2015). http://dc.engconfintl.org/polymer_rx_eng_IX/36