“…1) Partial differential equations solvers (referred to here as direct simulations, DS) using the finite element method (FEM), the finite volume method (FVM), or other methods on discrete meshes [e.g. Pruess et al, 1999, Diersch, 2013, Tatomir, 2013, Lang et al, 2014, Hyman et al, 2015, Settgast et al, 2017. 2) Analytical approximations of the equivalent permeability of the fractured rock, based on fracture and fracture-network properties [e.g.…”