This article investigates the use micro capsules, containing a gelling agent hydroxypropyl cellulose (HPC), to alter flow paths in porous media. The aim is to preferentially block off high permeability regions, thereby diverting the flow into adjacent un-swept low permeability regions. Micro capsules with 2-7 mu m in diameter were made by polymer precipitation through solvent evaporation using poly(4-vinyl pyridine) (PVP) as the shell material. A customised flow Lank was constructed to facilitate porous media flow and both single and dual permeability experiments were conducted. Even without gelling agent, the micro-capsules gradually blocked the pore throats of the glass beads network. Following acidification a drop in permeability was observed. This was because swelling of the PVP shell constricted the pore throats. The permeability drop was observed to be more significant for low permeability regions. Flowing micro-capsules through the tank with two permeability regions in parallel allowed the high permeability region to be selectively blocked. (C) 2014 Elsevier Ltd. All rights reserved.