Unconventional heavy oil ores (UHO) have been considered an important part of petroleum resources and an alternative source of chemicals and energy supply. Due to the participation of water and extractants, oil–solid separation (OSS) and oil–water separation (OWS) processes are inevitable in the industrial separation processes of UHO. Therefore, this critical review systematically reviews the basic theories of OSS and OWS, including solid wettability, contact angle, oil–solid interactions, structural characteristics of natural surfactants and interface characteristics of interfacially active asphaltene film. With the basic theories in mind, the corresponding OSS and OWS mechanisms are discussed. Finally, the present challenges and future research considerations are touched on to provide insights and theoretical fundamentals for OSS and OWS. Additionally, this critical review might even be useful for the provision of a framework of research prospects to guide future research directions in laboratories and industries that focus on the OSS and OWS processes in this important heavy oil production field.

In the heavy petroleum industry, the development of efficient demulsifiers for the effective breaking of interfacially active asphaltenes (IAA)-stabilized water-in-heavy oil (W/HO) emulsions is a highly attractive but challenging goal. Herein, a novel nitrogen and oxygen containing demulsifier (JXGZ) with strong hydrogen bonding has been successfully synthesized through combining esterification, polymerization and amidation. Bottle tests indicated that JXGZ is effectual in quickly demulsifying the IAA-stabilized W/HO emulsions; complete dehydration (100%) to the emulsions could be achieved in 4 min at 55 °C using 400 ppm of JXGZ. In addition, the effects of demulsifier concentration, temperature and time on the demulsification performance of JXGZ are systematically analyzed. Demulsification mechanisms reveal that the excellent demulsification performance of JXGZ is attributed to the strong hydrogen bonding between JXGZ and water molecules (dual swords synergistic effect under hydrogen bond reconstruction). The interaction of the “dual swords synergistic effect” generated by two types of hydrogen bonds can quickly break the non-covalent interaction force (π-π stacking, Van der Waals force, hydrogen bonds) of IAA at the heavy oil–water interface, quickly promote the aggregation and coalescence of water molecules and finally achieve the demulsification of W/HO emulsions. These findings indicate that the JXGZ demulsifier shows engineering application prospects in the demulsification of heavy oil–water emulsions, and this work provides the key information for developing more efficient chemical demulsifiers suitable for large-scale industrial applications.

In the production process of the heavy oil industry, efficiently demulsifying water-in-heavy oil (W/HO) emulsions can effectively prevent the negative effects of emulsion corrosion on equipment, increase costs, reduce oil quality, and pollute the environment. Herein, polyether demulsifier complexes (PDC) were obtained by compounding fatty alcohol nonionic polyether (FAP) with perfluoropolyether (PFPEA, [CF₃O(CF₂CF₂O)_nCF₃]) through a simple physical blending method. The experimental results demonstrate that PDC exhibited outstanding demulsification performance for W/HO emulsions across varying temperatures: At 60 °C and 400 ppm dosage, PDC achieved complete dehydration (100%) within just 2 min, showing significantly faster demulsification kinetics compared to FAP and PFPEA. Even at the reduced temperature of 40 °C, PDC maintained effective demulsification capability, achieving complete phase separation within 6 min. These findings collectively establish PDC’s superior demulsification efficiency for W/HO emulsions, with particularly remarkable performance under challenging low-temperature conditions. Research on the demulsification mechanism indicates that PDC achieves efficient demulsification performance due to the synergistic effect the synergistic effect of FAP and PFPEA to effectively destroy the non-covalent bonds (hydrogen and π–π stacking) of interfacially active asphaltenes (IAA) at the oil–water interface, thereby achieving demulsification of W/HO emulsion. PDC with outstanding demulsification ability exhibits significant potential for practical applications in heavy crude oil–water emulsion treatment, and this work can provide insights for developing new composite demulsifiers for petroleum production.