Cooperative transport of emulsions in porous media*

Transport of soft and deformable materials in confinement is ubiquitous in geological flow. As an example, the transport and retention of individual dispersed fluid blobs in porous media has been explored from the perspective of the balance between capillary and viscous forces at the interfaces of fluids. However, the network connectivity, interfacial interactions, and cooperative transport of a dispersed phase are not reflected in the transport models of fluids. Here, we investigate the transport of emulsions in a micromodel of porous medium using microfluidics and optical imaging. By varying the size, concentration, and injection rate of the emulsions we observe that large and deformable emulsions are essential in the mobilization of small and trapped emulsions. In contrast with the bulk transport measurements, our pore-level transport data indicates that emulsions are more likely to be mobilized due to clogging of neighboring pores than single droplet transport.