Experimental and Numerical Simulation Studies of the Zwitterionic Polymer for Enhanced Oil Recovery

Abstract

This study presents a comprehensive investigation into the synthesis, characterization, and performance evaluation of zwitterionic polymers for enhanced oil recovery (EOR) applications. Three zwitterionic copolymers, which contains positively and negatively charged groups, designated as zPAM 1, zPAM 2, and zPAM 3, were synthesized and subjected to a series of analytical techniques to validate their successful synthesis and assess their properties. Fourier-transform infrared (FTIR) spectroscopy confirmed successful synthesis through characteristic peaks of N–H (3319–3338 cm⁻¹), C=O (1639–1662 cm⁻¹), and sulfonate groups (1113–1189 cm⁻¹). Proton nuclear magnetic resonance (1H NMR) spectra further verified the incorporation of zwitterionic units into the polymer backbone. Dynamic light scattering (DLS) revealed high molecular weights ranging from 598 to 734 kDa, confirming their suitability for EOR applications. Scanning electron microscopy (SEM) showed distinct morphologies, with zPAM 1 and zPAM 2 exhibiting highly ordered network structures conducive to enhanced stability and mechanical integrity. Rheological experiments demonstrated typical shear-thinning behavior across all copolymers. Among them, zPAM 1 exhibited the highest viscosity values, with a 30 % viscosity increase as salinity rose from 100,000 to 200,000 ppm and a 60% viscosity loss as temperature increased from 25 °C to 60 °C. Coreflooding experiments, conducted at 63 °C and 200,000 ppm salinity using a polymer concentration of 1000 ppm, revealed that zPAM 1 achieved a total oil recovery factor of 56.5%, compared to 52.3% for commercial hydrolyzed polyacrylamide (HPAM). The higher pressure drop observed during postflush indicated stronger mobility control for zPAM 1. The superior EOR performance of zPAM 1 is attributed to its optimized molecular architecture, enhanced salinity tolerance, and favorable viscoelastic behavior arising from its DMAPMAPS-based zwitterionic structure. These findings underscore the importance of molecular design and structural composition in influencing the rheological behavior and performance of zwitterionic polymers in EOR applications. The insights gained from this study contribute to a deeper understanding of zwitterionic polymers' potential for enhancing oil recovery efficiency and sustainability, discovering new ways for further research and optimization in this field.