Advances in chemical demulsifiers for oilfield applications: a comprehensive review

The increasing complexity of crude oil emulsions, driven by advanced extraction techniques and stringent environmental regulations, poses significant challenges to the petroleum industry. While existing reviews have summarized demulsifier types and mechanisms, a critical gap remains in systematically evaluating the performance, scalability, and environmental trade-offs across emerging demulsifier classes. This review provides a comprehensive and critical analysis of chemical demulsifiers for oilfield applications, uniquely integrating classical mechanisms with recent advances in bio-based, nanomaterial, and smart responsive systems. Key contributions include: (1) a unified classification framework that clarifies the relationship between molecular structure and demulsification performance; (2) a critical evaluation of current research limitations, highlighting discrepancies between laboratory findings and field applicability; (3) quantitative comparisons of demulsifier efficiency, cost, and environmental impact; and (4) a forward-looking assessment of AI-driven design, stimuli-responsive materials, and circular economy strategies. By addressing these knowledge gaps, this review offers a structured reference for researchers and engineers aiming to develop next-generation, sustainable demulsification technologies.