Investigation of microbubble CO2 enhanced oil recovery: Numerical simulation

Microbubble (MB) flooding provides a potent means of suppressing gas channeling and enhancing mobility control in CO2-Enhanced Oil Recovery (CO2-EOR). Unlike conventional continuous gas injection, dispersed microbubbles can leverage the Jamin effect to improve sweep efficiency. This study investigates the transport mechanisms and oil-displacement behavior of CO2 microbubble in fractured, low-permeability reservoirs using high-fidelity Euler-Lagrange pore-scale simulations. We examined the impact of bubble diameter (10–90 μm) and carrier fluid viscosity on displacement efficiency within complex pore networks (Types I, II, and III). The simulation results indicate that optimized MB injection significantly delays gas breakthrough from 0.87 pore volumes (PV) in conventional CO2 flooding to 3.86 PV, increasing final displacement efficiency to 94–95% when using 10–30 μm bubbles. Mechanistic analysis reveals that uniform MB dispersion dynamically redirects flow from high-permeability channels into previously bypassed zones via capillary blocking. Furthermore, the high effective viscosity of the microbubble dispersion (∼243.5 cP) stabilizes the displacement front, suppressing viscous fingering and minimizing vortex formation in tortuous pore geometries. Parametric optimization suggests a coupled size-viscosity window—specifically 20–30 μm bubbles at effective viscosities of ∼220–250 cP—provides an optimal balance between throat penetration and mobility control. These findings offer theoretical support for the field-scale deployment of MB-assisted CO2-EOR, demonstrating how tailored bubble rheology can mitigate operational risks and maximize recovery in heterogeneous strata.