Flow Channeling, Dissolutional Growth, and Preferential Flow of Fractures in Karst formation: Insights from Reactive Transport Modeling

Fractured and karstified carbonates often serve as major aquifers and hydrocarbon reservoirs. Water-rock interactions within variable aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of fractures over time. Numerical modeling offers a valuable tool for comprehending the spatial and temporal evolution of karst reservoirs. This work aims to present a comprehensive model to reveal percolation characteristic and dissolution process of stochastic primary fracture systems in carbonate formation. Based on the embedded discrete fracture model, a multi-scale modeling approach is proposed to describe fracture networks with different topologies and various apertures. This model is verified against preexisting numerical models. Simulation results shows that the mechanisms of flow focusing and reactive infiltration instabilities determines fracture dissolutional propagation. Patterns of local dissolution-induced alterations related to fracture permeability, hydraulic conductivity and extensive dissolution appear in fracture tips and intersections.