Microfluidic systems for the analysis of the viscoelastic fluid flow phenomena in porous media

In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/ expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application

The effects of heterogeneity and wettability on oil recovery from laminated sedimentary structures

The sedimentary structure and wettability of clastic rocks at the laminaset scale may have an important influence on oil recovery by waterflooding. Previous work from this laboratory reported results for oil displacements in water-wet laminated systems. In this paper, results from a full cycle of drainage-imbibition floods in a cross-laminated rock slab are reported where the wettability of the slab was changed by ageing the system with a "synthetic crude oil". The distribution of fluid saturation was monitored using CT scanning techniques. The main purpose of this work is to investigate the effects of both the laminaset heterogeneity and wettability alteration on the displacement efficiency and oil trapping mechanisms for such systems. Results from from these floods are compared with previous findings for water-wet laminated system. In these altered wettability experiments, the recovery efficiency significantly increased, due to the slab becoming more oil-wet. In contrast to the strongly water-wet case, an analysis of the remaining oil saturation shows that (a) no significant oil trapping occurred behind low permeability laminae in this flood, and (b) there was a higher remaining oil in the low permeability regions. Numerical simulations were performed to help our understanding and interpretation of the wettability changes. An excellent match of experiment with numerical simulation was obtained for a particular model case with the lower permeability laminae being more oil-wet than the higher permeability ones in general. We have termed this a heterogeneously-wet (or het-wet) system. To our knowledge, this is the first time that such behaviour has been demonstrated and analysed in detail. Copyright 1996, Society of Petroleum Engineers, Inc