Reactive Transport in Porous Media
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In this thesis, we show how the common equations for flow in porous media can be expanded to account for geochemical reactions. Furthermore, the complications arising when solving the new equations numerically are described and explained. Specialised methods that alleviate the difficulties are then introduced, and discussed with respect to robustness and convergence properties. Much attention is directed to ways of reformulating the equations, in order to make them more amenable to numerical treatment. Also, the fact that chemical reactions introduce stiffness to the system is adressed. Diagonally implicit Runge-Kutta methods, which are commonly used to combat stiffness, are evaluated with respect to their usefulness in CO2 sequestration simulations. Finally, we have applied the methods to several test cases, some including complex mineralogies, to illustrate the strengths and weaknesses of the different numerical approaches.