Polymer Molecular Architecture As a Tool for Controlling the Rheological Properties of Aqueous Polyacrylamide Solutions for Enhanced Oil Recovery

Abstract

The controlled synthesis of high molecular weight branched polyacrylamide (PAM) has been accomplished by using atomic transfer radical polymerization (ATRP) of acrylamide (AM) in water at room temperature. Halogen-functionalized aliphatic polyketones acted as macroinitiators in the polymerization. The obtained branched polymers were used in water solutions to study the effect of the molecular architecture on the rheological properties. For comparison purposes, linear PAM was synthesized by using the same procedure. The intrinsic viscosities and light scattering data suggest that the 13-and 17-arm PAMs are more extended in solution compared to the linear, 4-arm, and 8-arm analogues, at equal total molecular weight. The comparison of linear and 4-, 8-, 12-, 13-, and 17-arm PAM in semidilute solutions demonstrated that the 13-and 17-arm PAM have the highest solution viscosity at equal molecular weight. Depending on the PAM molecular weight and concentration, a significant (as much as 5-fold) increase in solution viscosity (at a shear rate of 10 s −1 ) is observed. The elastic response of aqueous solutions containing the polymers critically depended on the molecular architecture. Both the 4-and 8-arm polymers displayed a larger phase angle value compared to the linear analogue. The 13-and 17-arm PAMs displayed a lower phase angle than the linear one. Ultimately, the rheological properties are dependent on the number of arms present. The combination of a higher hydrodynamic volume and higher entanglement density leads to an improved thickening efficiency (for N ≥ 13, N being the average number of arms). The improved thickening efficiency of the branched (N ≥ 13) PAMs makes these polymers highly interesting for application in Enhanced Oil Recovery and drag reduction.

Architectural Effects on the Solution Behavior of Linear and Star Polymers in Propane at High Pressures

“…These researchers concluded that the arms of the star polymer stretch to best accommodate both intra-and interarm repulsions. Wever et al 16 also report that the arms adapt a more stretched conformation with an increase in number of arms in a star polymer. The increased free volume of the LMA-MMA 50 star polymer relative to its copolymer analogue apparently has a more dominant effect on the phase behavior than the MMA−propane energetic mismatch that is magnified with the large number of MMA groups within the star polymer.…”

Free-Radical Graft Polymerization onto Starch as a Tool to Tune Properties in Relation to Potential Applications. A Review

“…According to Perrier [40], the past years of research have now allowed RAFT to become a tool in which new complex and functional materials can be made. A relevant example, although at laboratory scale, is the synthesis of polyacrylamide with a well-defined branched structure for applications in chemical enhanced oil recovery, as developed within our Groningen University Product Technology group by Wever [44] and more recently by v. Mastrigt [45]. Other recent examples illustrate the possibility of using photo-initiated RAFT polymerization in emulsion, further expanding its scope [46,47].…”

Opportunities of improved development of high-viscosity oil pool in Perm kray

“…Для продвижения по пласту используют растворы полимеров, высокая вязкость ко-торых позволяет применять оторочки ми-целлярными растворами меньших объе-мов. Хорошая смесимость мицеллярных растворов с водой и нефтью, а также дос-таточно низкое поверхностное натяжение на границе раздела создают благоприятные условия для вытеснения нефти [14,15].…”

“…Рассмотрены возможности приме-нения полимерного заводнения, закачки мицеллярных растворов и теплоносителя. Потокоотклоняющие технологии и поли-мерное заводнение будут наиболее эффек-тивны для данной залежи с высоковязкой нефтью [15][16][17].…”