A Comparison of Two Numerical Models for Flow in Fractured Porous Media and the Impact of Fracture Intersection Cell Removal

Abstract

The simulation of flow and transport in fractured porous media is crucial to improve understanding and viability of geothermal energy. It is also challenging, due to complex geometries and large scale differences. In this thesis, we compare two numerical methods developed to meet these needs; a Finite Volume method and a Mixed Finite Element method. We analyse their behaviour based on a collection of test cases. In addition to studying the produced pressure solutions, we perform transport simulations to reveal local behaviour through accumulation. We take particular interest in the intersections of fractures and the possibilities in removing the intersection cells from the spatial discretization, improving condition numbers and relaxing time step restrictions. We identify some dangers in eliminating the cells before the flow is solved, and instead propose a procedure to be applied between the flow simulation and the transport simulation.