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Transport in heterogeneous porous media

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Lunch in open plan area

In practice, many porous media of interest, particularly in the natural world, are highly heterogeneous. Often field scale data displays significantly different behaviour to simple laboratory experiments and homogeneous mathematical models. It is well known that medium heterogeneities on a local scale have an important impact on the effective large scale behaviour of solute transport. Therefore, understanding the influence of hetereogeneity on flow and transport processes within a porous medium is critical to a better understanding of real life observations. Using stochastic modelling techniques, we have developed upscaled ‘homogeneous’ mathematical models that aim to capture the influence of heterogeneity. In this seminar we present the results on three areas of interest:

a) The influence of spatial heterogeneities and temporal fluctuations on the transport of a passive solute, which has practical implications for the transport of subsurface contaminants. In particular we examine the enhanced mixing that is observed and quantify it by calculating effective dispersion coefficients that depend on the properties of the medium and flow.

b) The influence of heterogeneities on multiphase flow. We study Buckley Leverett (idealised immiscible two phase displacement) flow in a heterogeneous porous medium under the influence of a temporally fluctuating flow field. We also examine the influence of buoyancy, which appears to significantly enhance ‘mixing’. This project is motivated by a desire to understand the influence of heterogeneities on multiphase flow, which has specific applications in CO2 sequestration and oil recovery.

c) The effect that variable flow paths (in heterogeneous and some homogeneous media) have on contaminant transport. Often, on the macroscale, the diffusion/dispersion of a passive tracer appears to behave in a non-Fickian manner. Using simple models we attempt to explain/quantify these observations by considering the fact that within a porous medium parcels that have been displaced over the the same distance in one dimension can have traveled along different flow paths and thus very different distances. While locally all transport will be Fickian these varying flow paths can lead to highly non-Fickian behaviour on the large scale.

This talk is part of the Institute for Energy and Environmental Flows (IEEF) series.

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