Magnetically activated microcapsules as controlled release carriers for a liquid PDMS cross-linker

Injecting water into a porous oil reservoir enhances oil sweep efficiency and leads to increased oil production, but due to the occurrence of fractures in water-flooded reservoirs, excessive water production is observed. Hence, water shut-off treatments are continuously investigated, albeit currently applied plugging materials still suffer from some disadvantages such as lack of selectivity and poor mechanical strength. In this work, we introduce a new plugging material consisting of vinyl-functional PDMS microspheres and magnetically activated microcapsules. This work focuses on the preparation and characterisation of microcapsules containing magnetite nanoparticles (MNPs), and liquid cross-linker in their core. The microcapsules are prepared via a phase separation technique, and it is established that the MNPs are located inside the microcapsules and that the shell remains nonporous, in which case the cross-linker is well protected before activating the microcapsules. While exposed to an alternating magnetic field, the MNPs generate sufficient heat to soften the polymeric shell, thereby leading to the efficient release of the cross-linker; moreover, the PDMS microspheres create a strong network, due to a cross-linking reaction. It is expected that this new approach will improve significantly the plugging process of fractures in matured reservoirs, which in turn will lead to higher oil recovery rates.