Multiscale Reservoir Simulation

In the conventional approach to reservoir simulation one starts with a fine-scale geomodel that may consist of several million grid blocks. This geomodel is then upscaled a few orders of magnitude so that it is possible to perform reservoir simulation. If more than one phase is present, upscaling is both time-consuming and not very robust. We propose to develop a new simulation scheme that may reduce the need for upscaling considerably. If successful, this may eventually have a strong impact on the reserv oir-modelling workflow and save a large number of man-hours. Our key idea is to combine an existing methodology called non-uniform coarsening with a novel multiscale simulation method. The non-uniform coarsening method is a method for computing simulat ion grid models that are finely gridded in high-flow regions and more coarsely in regions with low flow. Dispite having many ideal properties, the direct applicability of the method to real 3D reservoir simulation is limited because it can induce very uns tructured coarse grids. Such grids often have large grid block aspect ratios that may severely degrade the accuracy of upscaling based reservoir simulations. The main purpose of this post-doc project is to develop a methodology for robust reservoir simul ation on high-resolution geomodels by using the non-uniform coarsening approach to construct the coarse grid for a mixed multiscale finite element method. The method is not particularly sensitive to the grid block aspect ratios and does not put any restri ction on the geometry of the grid blocks. In fact, the mixed FEM base functions are constructed so that they adapt to the local property of the differential operator and automatically account for the geometry of the grid blocks. This mixed FEM therefore h ave features that remove the main limitations with the non-uniform coarsening methodology. The project is related, but complementary, to the SIP proposal no. 158908/420.