CO₂/brine multiphase flow in micro-fractured rocks under capillary-viscous displacement pattern

Microfractures are widely distributed in natural rocks, but are usually simplified or ignored in models, leading to a failure to reflect micro-flow behavior accurately. To investigate the behavior of CO₂ flow in rocks with microcracks accurately, we developed an approach for generating models containing random and irregular microfractures. Expanding the thresholding Gaussian random fields method to ensure the ability for generating realistic microfracture morphology with controlled complexity and width. For contact detection, Matrix filling was applied to transform the continuous problem into a discrete one, ensuring the accuracy of detection and parameter updating. Phase field method was applied to conduct pore-scale simulations using this fractured model to analyze the effects of capillary number (Ca), wettability, and fractures on CO₂ flow behavior under capillary-viscous displacement pattern. Compare with model without fractures, through-going fractures reduced sequestration efficiency owing to enhancing the heterogeneity of flow. Specifically, it restricted the ability of CO₂ to break through fractured regions for a wider distribution especially at high Ca. Consequently, sequestration enhancement need lower Ca to enhance capillary imbibition in fractured model, while higher Ca is necessary to enhance viscosity fingering in non-fractured models. Our proposed modeling approach provides an effective guide for investigating CO₂ flow behavior in rocks at microscopic scale.