Wormholing in fractured porous media: Nonlocal reactive flow modelling based on peridynamic theory

Fractured porous media with primary and secondary fractures play a key role in the propagation of wormholes . In this study, we present a nonlocal reactive flow framework, which is based on peridynamic (PD) theory, for modelling acid injected into fractured porous media. The normalised damage index and the fracture bond damage index ratio are proposed to investigate the influence of fractures on the wormhole patterns and optimal injection rate . The results of matrix acidification in fractured porous media with different fracture apertures demonstrate that the PD reactive flow model can predict acid transport in fractures and capture complex porosity evaluation processes. The parallel fractures more easily become the dominant wormhole propagation paths , whereas more branches connected to the perpendicular fractures are observed. A series of 2D radial reactive flows with different fracture propagation rates is conducted. The optimum injection rate decreases as the fracture propagation rate increases. When acid is injected at the optimum injection rate, the pore volume of acid to breakthrough (decreases to lower than 1.24) and acid leak-off are minimal (the fracture bond damage index ratio increases to higher than 44.8%). These findings may contribute to the understanding of wormholing in fractured porous media, with implications for reactive flow-related processes such as CO 2 sequestration, karst system formation, and carbonate reservoir stimulation .