This article investigates the possibility or using micro-capsules, with a gelling agent, hydroxypropyl cellulose, in the core, during enhanced oil recovery. The aim is to block off high permeability regions of a formation known as thief:zones, thereby diverting the chase injection water into adjacent unswept low permeability regions. Temperature triggered micro-capsules were made by polymer precipitation through a solvent evaporation method, with poly(lactic-co-glycolic) acid as the polymer shell. Release studies with methylene blue demonstrated the temperature induced release from these micro-capsules. A customised tank was made to allow porous media flow and single permeability experiments were conducted. Even without the gelling agent, the micro-capsules gradually blocked the ballotini pore network. However, by varying the tank temperature, a drop in permeability was observed when the capsules released their core. Experiments with two permeability regions showed that the micro-capsules clogged up the high permeability layer more than the low permeability region. (C) 2013 Elsevier Ltd. All rights reserved.