efsim (Embedded Fractures SIMulator) is a code base for simulating flow and transport in porous media, where fractures are modeled as lower-dimensional surfaces embedded in the surrounding media.

This code base constitutes the computer implementations developed as a part of the PhD project "Reservoir Simulation in Heterogeneous and Fractured Reservoirs", conducted at NTNU, Trondheim, in the period August 2013 - March 2018. PhD thesis.

Disclaimer: This code base is distributed in the hope that it will be useful, but without any warranty.

The code base contains implementations to solve single-phase flow coupled to advective transport of a concentration in heterogeneous and possibly fractured porous media. The solver is sequential with three main steps:

1. The flow problem (Darcy's equation) is solved by a classical continuous Galerkin finite element method
2. Locally conservative fluxes are computed by a postprocessing step
3. The transport problem (advection equation) is solved by a low-order finite volume method with upwinding (or equivalently the lowest order discontinuous Galerkin finite element method)

There are two main application programs:

• spsim: Slightly compressible single-phase flow coupled to advective transport in heterogeneous porous media (2/3D)
• efsim: Incompressible single-phase flow coupled to advective transport in heterogeneous and fractured porous media (2D)

More details are given in the references listed below.

• LH Odsæter, MF Wheeler, T Kvamsdal, and MG Larson. Postprocessing of non-conservative flux for compatibility with transport in heterogeneous media. Computer Methods in Applied Mechanics and Engineering 315:799-830 (2017)
• LH Odsæter, T Kvamsdal, MG Larson. A simple embedded discrete fracture-matrix model for a coupled flow and transport problem in porous media. arXiv:1803.03423 (2018)

Please cite one or both if you are using this code.

efsim uses CMake and is only verified to work in Unix-environments.

efsim is based on the open source finite element library deal.II, which is well documented.

• deal.II, version 8.4.1. Installation instructions
• trilinos, version 11.4.1. Installation instructions

mkdir build
cd build
cmake -DDEAL_II_DIR=/path/to/deal.II ../
make

Optionally,

make test

will run a series of integration and benchmark tests to check if the code runs correctly.

After a successful installation, the build directory should now contain a number of binaries. The two main application programs are spsim and efsim, see Introduction above. These are run with the commands

./spsim input_spsim.prm

or

./efsim input_efsim.prm

Examples of input files are found in the base directory input_files. For documentation of the input files, run

./spsim -help
./efsim -help

Known pitfall: The programs assume that the directory they are called from contains a subdirectory output, where result files are stored. An exception dealii::StandardExceptions::ExcIO is called if not.

The main classes are briefly described below.

Problem specific functions are found in ProblemFunctions.h