Importance of discrete fracture network structural properties on incipient karst genesis

Even though speleology allows to map the geometry of different cave systems, the majority of these systems remain unreachable underground. It has been observed that karst cavities often develop along features such as fractures and bedding planes in limestone reservoirs. In this study, we use a reactive transport model that simulate dissolution processes in fracture networks to investigate the effect of discrete fracture network structural properties on incipient karst network under different boundary conditions (constant head versus constant rate condition, diffuse versus concentrated recharge condition). We focused on single fracture (with/without cementation) and ladder like fracture networks which are common on limestone. Results showed that fracture networks properties have a considerable effect on the final geometry of dissolved wormholes. For instance, the presence of cement on a single fracture results on more tortuous and curvilinear wormholes. Moreover, anisotropy of the fracture network leads into the formation of anisotropic incipient karst geometries. Also, the type of fracture intersections plays a role in the final incipient karst conduit geometry and topology. Finally, the type of BC remains a major factor that governs dissolution processes.