Water control in oil and gas wells is crucially needed in many oil and gas producing wells. Recent studies have indicated that chemicals, that are soluble in oil without a chemical reaction but react and form gels upon contact with water, may block water-bearing zones with little risk of damaging the oil-bearing zones. The chemical is initially mixed with oil. The gelation process involves the partitioning of the chemical out of the oil phase into the water phase. A heterogeneous reaction occurs (hydrolysis and condensation) between gelant and water, leading ultimately to gelation. The aim of this study is to gain greater insight into the coupled mass transfer and gelation process both in bulk and in porous media. We use Nuclear Magnetic Resonance (NMR) imaging techniques to conduct both qualitative and quantitative analyses. The discrimination between the chemical components is mainly based on relaxation times T1 and T2. Bulk measurements are performed to study the mass transfer-reaction mechanisms in an idealized setting. Mass transfer rates and gelation times are estimated as functions of physical parameters (temperature, concentrations etc.). The chemical is then applied in idealized porous media (glass bead packs) containing two phases. Highresolution images are used to reveal the reaction-mass transfer phenomena on the (macro-) pore scale. The results prove to be very promising for further investigations with the NMR methods.

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