Hydrophobically Modified Chitosan‐Based Polymers for Enhanced Oil Recovery

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The upstream petroleum industry significantly contributes to environmental pollution through the use of fossil‐derived chemicals. This study explores the potential of green alternatives by synthesizing and evaluating chitosan‐based polymers for enhanced oil recovery (EOR) applications. A native chitosan salt (S0) and its hydrophobically modified derivatives (S1–S4), grafted with linear alkyl chains (C5–C8), were synthesized and systematically characterized. Key parameters investigated include thermal stability in seawater, interfacial tension (IFT), rheological behavior, and wettability alteration of carbonate rock surfaces. The performance of these materials was found to correlate with their critical aggregation concentration (CAC) and hydrophobicity. While the unmodified chitosan (S0) exhibited no interfacial activity, HM‐chitosan displayed surfactant‐like behavior with characteristic L‐shaped IFT profiles. Despite limited viscosity enhancement, all HM‐chitosan significantly reduced water contact angles by up to 46%, indicating effective wettability alteration. These findings show the promise of HM‐chitosan as an environmentally friendly EOR agents due to their biocompatibility, structural tunability, and surface activity. The study establishes a fundamental framework linking molecular structure, CAC, and performance, supporting future applications in porous media systems.