Simulation of Steam-Water Phase Transitions (2013-2018)
Modeling of geothermal reservoirs poses significant difficulties for nonlinear solvers in reservoir simulation. This research focuses on designing novel numerical algorithms to overcome these nonlinear difficulties. These difficulties arise from the strong coupling between the mass and energy conservation equations. This strong coupling results in an apparent "negative compressibility" for blocks that have both liquid and steam phases. This "negative compressibility" presents significant difficulty for the standard fully implicit approach. An example of this is shown the figure, where the Newton paths diverge depending on the initial guess to the problem. To overcome this, different sequential formulations and nonlinear preconditioners are investigated and tested using the AD-GPRS (Automatic Differentiation-General Purpose Research Simulation) Framework.