Novel Green Strategy Based on Combination of CO2/Protic Poly(ionic liquids) for Enhancing Crude Oil Recovery

Carbon dioxide (CO₂) contributes to erratic climate changes as a greenhouse gas in the atmosphere, highlighting the need for effective carbon capture, storage, and conversion strategies. This study introduces a green solvent approach using protic poly(ionic liquids) (PPILs) for CO₂ chemisorption to improve enhanced oil recovery (EOR) methods through gas/polymer flooding. The PPILs were synthesized by copolymerizing quaternized triethanolammonium 2-acrylamido-2-methylpropanesulfonate (QAMPS) with an equimolar amount of triethanol ammonium acrylate (QAA) via radical polymerization, resulting in QAMPS/QAA copolymers. Similarly, QAMPS was copolymerized with equimolar amounts of 2-hydroxyethyl methacrylate (HEMA) or N-vinylpyrrolidone (VP) to produce QAMPS/HEMA and QAMPS/VP protic PILs. The study examined the chemical structure, thermal degradation stability, and transitions. The thermal degradation of QAMPS/QAA, QAMPS/HEMA, and QAMPS/VP was obtained at initial degradation temperatures of 210, 275, and 150 °C, respectively. The rheological properties of these PPILs to assess their effectiveness in CO₂ solubilization, absorption, and desorption at both atmospheric and high pressures (800 psi) in formation water for potential application in EOR gas/polymer flooding strategies were examined. Additionally, the research explores the dynamics of CO₂ uptake by PILs and the ensuing alterations in their viscosity, which are crucial for enhancing the performance and success of EOR processes. Flooding on a 1D sandstone model revealed oil recovery rates of 38.9% for QAMPS/HEMA, 35.3% for QAMPS/VP, and 35% for QAMPS/QAA, relevant to residual oil saturation (%S_or).