Efficient oil-water separation is essential for treating produced fluids in petroleum engineering. This study investigates performance enhancement in hydrocyclones coupled with particles through theoretical analysis, visualization experiments, and numerical simulations. A critical model for oil droplet-particle collisions was established, revealing that smaller particle diameter, larger rotational radius, and smaller contact angle favor stable adsorption. Visualization experiments confirmed that particles promote droplet migration toward the hydrocyclone center, forming stable droplet-particle complexes at low rotational speeds while rebound dominates at higher speeds. A discrete element model based on the Johnson-Kendall-Roberts (JKR) adhesion theory was developed and validated, achieving a repose angle error of only 0.24%. Numerical results demonstrate that oleophilic particles significantly enhance droplet adhesion and improve overall separation efficiency by 8.19 percentage points, achieving 79.23% efficiency for 67 μm droplets (29.68 points higher than conventional hydrocyclones). These findings offer theoretical and practical support for optimizing and applying hydrocyclones coupled with particles in oilfield fluid treatment.

A minihydrocyclone (MHC) is known for its higher separation efficiency, particularly for fine or ultra-fine particles. However, the exact mechanism for enhancing the separation efficiency of MHCs has not been fully elucidated. This literature review fills the existing gap by comprehensively reviewing characteristics of the flow field inside MHCs, metrics of separation performance, applicable research methods, influence of physical and operating parameters, and provides references for future design and applications. Among them, the metrics of separation performance include grade separation efficiency, total separation efficiency, cut size, pressure drop, separation sharpness, and the fish hook effect, etc. This is the first time to comprehensively review the differences between MHCs and conventional hydrocyclones (CHCs) based on the above characteristics and metrics and analyze the separation advantages of MHCs. The fluid in MHC exhibits larger centrifugal acceleration, poor symmetry of tangential velocity, higher proportion of the wall friction loss, more obvious amplitude of partial sway of the air core, and smaller ratio of the locus of zero vertical velocity height to the total length of MHC. Challenges and further work on MHCs are also discussed in terms of potential applications and needed improvements.