Reservoir mesh creation using extended anisotropic, geometry-adaptive refinement of polyhedra

One example herein involves a method that includes identifying, based on a received reservoir specification: a set fractures including 2.5 dimensional (2.5D)-permitting fractures; and other fractures. The method further includes generating an intermediate reservoir model including an extrusion mesh which models the 2.5D-permitting fractures in a three-dimensional (3D) space. In response to determining that cells in the mesh should be refined in a direction within the 3D space, the method anisotropically refines cells in the mesh corresponding to the other fractures. The method also includes resolving a fracture network within the intermediate reservoir model using the refined cells and then generating a reservoir earth model using the fracture network.