Multi-scale meshing for 3D discrete fracture networks

Resumo

The geometric description of a Discrete Fracture Network (DFN) in the context of multi-scale meth-
ods, involves the ability of inserting multiple fractures in a predefined coarse mesh, while building volumetrical

elements of smaller scale around the surface of these fractures in order to create sub-meshes inside the coarse
elements. This paper presents an approach for automatic finite element meshing of fractured reservoirs suited to
Multi-scale Hybrid-Mixed methods (MHM). The code is written in C++ and largely relies on two open source

finite element libraries: NeoPZ and Gmsh. The main steps to the method involve: locating intersections and re-
fining elements at those points, building a data structure that associates each element of a fracture surface to the

coarse volume that encloses it, and then generate a sub-mesh of fine elements around the fractures to fill these
coarse elements, without altering originally defined nodes in the coarse mesh. In order to improve the quality of
geometrical elements to be generated, strategies of moving intersection points and features simplifications are also
presented. Results show that the proposed technique can efficiently construct adequate 3D meshes. While relying

on neighbourhood information and consistent element topologies available from NeoPZ’s geometric meshes, en-
ables optimization of multiple algorithms of geometric search that would, otherwise, require a considerable amount

of floating-point operations.