A New Method to Develop Homogeneous and Heterogeneous Porous Micromodels Applicable to Enhanced Oil Recovery and Flow Visualization Experiments

In this paper, a new method to fabricate micromodels having homogeneous and heterogeneous porous structures is reported to gain fundamental insight into the flow through porous media. The technique of microparticle image velocimetry (PIV) is used to map the pore-scale velocity field inside the micromodels. A thin perforated metal sheet composed of uniformly distributed circular holes is used as the master pattern, and the replica of the negative of this perforated sheet is transferred to a polydimethylsiloxane (PDMS) substrate using a method similar to the soft lithography. This method allows an efficient fabrication of micromodels having different porosity by adjusting and selecting the perforated sheets of different hole sizes. The prepared micromodels were tested for its applicability and reliability by carrying out the measurements of pore-scale velocity distribution using the micro-PIV technique. The experiments with micromodels with high porosity but different grain arrangements showed qualitative as well as quantitative differences in the velocity field. The pressure drop across the two ends of micromodel is also measured. The variation of pressure difference with the flowrate is found to be nonlinear with a significant effect on the patterns of micropillars. However, at low porosity, the variation of pressure difference with the flowrate is found linear and there is almost no influence of the micropillar patterns. The flow visualization measurements are also conducted with the dual porosity micromodels, and the flow patterns were examined by analyzing the velocity vector maps.