The role of porosity for transport block-upscaling in a clay-rich sedimentary formation

摘要

Large-scale numerical transport models are needed for many applications in hydrogeology. Known local-scale parameters have to be transferred to a larger numerical grid scale in order to model the large-scale behaviour correctly. Classical methods of upscaling do not alter the porosity of upscaled models. We study advective transport on successively (block-) upscaled 3-D heterogeneous hydraulic conductivity fields of a strongly heterogeneous formation. We analyse the resulting breakthrough curves and, particularly, the changes of early arrival times, which give us a measure of mobile porosity of the upscaled model. We find the early arrival time delayed when homogenizing the hydraulic conductivity field. To account for this delay the mobile porosity of the upscaled model has to be reduced. This is an indicator that multiple-rate mass transfer is an excellent tool for upscaling strongly heterogeneous aquifers.