A node-splitting discrete element model for fluid-structure interaction

A new discrete element model (DEM) has been developed for the purpose of simulating dynamic fracturing driven by the internal generation of fluids in low permeability elastic solid bodies. The elastic material is represented by a network of nodes connected by springs, and fracture nucleation and propagation is implemented by splitting nodes and reconnecting the spring network. This produces realistic fracture shapes, and reduces lattice artefacts compared with DEM models in which fracturing is implemented by breaking/removal of springs. Fracture volumes and surfaces are explicitly represented in terms of the voids in the reconnected spring network, simplifying the coupling between mechanical deformation and fluid pressure in the fractures, and facilitating the modelling of fluid transport. The model is illustrated by applying it to fracturing driven by internal fluid generation in an impermeable quasi two-dimensional system. This is relevant for many geological processes, including primary migration of oil and gas in low-permeability source rock. The model may also be adapted to hydraulic fracturing processes, which are of industrial interest in connection with unconventional oil and gas production.