•2 min read•from Frontiers in Marine Science | New and Recent Articles
Characterizing immiscible waterflooding in intersecting rough-walled fractures using a phase-field method
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Characterizing immiscible waterflooding within fractured reservoirs presents a significant challenge in deep energy development. This study utilizes a phase-field method to model two-phase displacement in three-dimensional rough-walled fractures, investigating the impact of intersection morphology and angle. Numerical results reveal fracture intersections as key bottlenecks, often intensifying viscous fingering and hindering stable displacement fronts. Intersection angle effects are geometry-dependent, with symmetrical, straight fractures demonstrating improved displacement efficiency and reduced residual oil accumulation.
The two-phase displacement in rock fractures is a critical scientific challenge in deep energy development projects, as well as in the safe operation of offshore and nearshore subsurface reservoirs, characterized by the intricate and dynamic flow patterns resulting from the complex fracture geometry and mutual interference between the two-phase fluids. The present study involves the construction of a three-dimensional rough fracture fine model using the fast Fourier transform and the Gaussian distribution method. The phase field-finite element method is employed to simulate the dynamic displacement of water-oil flow and the evolution of the water-oil interface, aiming to investigate the impact of intersection morphology and angle on the water-oil displacement efficiency in rough-walled fractures. The numerical results indicate that fracture intersections are key bottlenecks for fluid flow. The phenomenon of viscous fingering intensifies after the fluid passes through the fracture intersection, making it difficult for the water to form a stable displacement front. The effect of intersection angle on oil displacement is strongly dependent on fracture geometry and does not follow a simple monotonic trend. Small intersection angles generally promote oil displacement in X-shaped fractures, whereas Y-shaped fractures exhibit more complex behavior, with the 120°case showing the lowest water volume fraction. V-shaped intersecting fractures form narrow channels at small intersection angles, which are the main type causing inefficient circulation and residual oil enrichment. Furthermore, fractures with a symmetrical structure and a nearly straight course are more conducive to improving displacement efficiency. Asymmetrical structures and fluid flow into complex fractures are more likely to lead to the accumulation of residual oil. These findings provide a mechanistic basis for multi-scale subsurface flow modeling and can support forecasting-oriented evaluation of preferential pathways, trapping zones, and flow bottlenecks in fractured geological environments.
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