Research progress on the treatment of polymer flooding produced water by flocculation/coagulation: A minin Review

In the middle and late stages of oilfield development, water becomes a critical medium for enhancing oil recovery. Most major oilfields have adopted polymer flooding and ternary composite flooding as primary extraction techniques. However, the increased recovery efficiency is accompanied by the production of large volumes of polymer flooding produced water (PFPW). This PFPW is characterized by its complex composition, containing not only high concentrations of suspended solids but also, more critically, stable emulsified oil. To address the challenges in PFPW treatment, this study first analyzed the reasons for the difficulty and stability factors of emulsified oil in PFPW, and then systematically reviewed the existing treatment technologies, with particular attention to flocculation/coagulation methods. The research elaborates on the mechanisms and performance of organic polymer flocculants, inorganic polymer coagulants, and composite flocculants, providing a comprehensive evaluation of recent progress in this field. Finally, this research provides a forward-looking perspective for the design of advanced flocculants/coagulants from three aspects to more effectively handle PFPW in oilfield operations.