Two-phase flow dynamics in 3D fractures: Influence of aperture, wettability, and fluid properties from Lattice Boltzmann Simulations

It is often assumed that using stratified patterns models capture adequately two-phase flow in fractures. However, recent studies indicated that a broader range of flow behaviors may occurs. This paper explores the impact of aperture and wettability on relative permeability in three-dimensional Berea fractures displaying moderate topological fluctuations. Using Lattice Boltzmann Method (LBM) simulations, we identify two distinct permeability regimes: at high apertures, permeability behavior aligns with that of parallel planes, while at low apertures, permeability decreases linearly due to fluid interactions with fracture surfaces. In weakly wet fractures, anomalous relative permeability behavior arises within specific aperture ranges, linked to the emergence of distinct flow structures. This phenomenon is primarily driven by interfacial tension, while wettability affects its onset, particularly at intermediate apertures. Furthermore, in non-wet fractures, fluid segregation at high apertures is governed by viscosity contrasts, where higher-viscosity fluids tend to flow more centrally, resembling Poiseuille flow. The results are particularly relevant to oil and gas recovery, highlighting the need for further investigations into interfacial tension effects in gas–liquid systems to enhance predictive models for fluid transport in fractured reservoirs.