Two-phase reactive transport of an oil-soluble chemical: An NMR study

An oil-soluble chemical (OSC) is a chemical substance which is soluble and chemically inert in oil, but reacts with water to form a gel. Application of an OSC can be found in oil- and gas production. An increased water production, which usually occurs in mature oil fields, can be remedied by injecting the OSC in the near-wellbore area. The OSC will then form gel in the porous rock which has high water saturation, thereby blocking the water flow. In this study, which is mainly experimental, the reactive transport processes were analyzed on a fundamental level, both in two-phase bulk systems and in porous materials. Advanced Nuclear Magnetic Resonance (NMR) methods were used. By measuring the NMR relaxation times of both hydrogen (in oil) and deuterium (in heavy water), the coupled mass transfer and gelation were characterized and quantified. The results showed that both in bulk as well as in sandstone the mass transfer of the OSC is driven by the hydrolysis reaction which is strongly dependent on pH and temperature. Also the coupled gel reaction is strongly dependent on these parameters. Finally, the effect of the formed gel on the permeability of the rock was quantified in order to determine the blocking capacity of the gel, with respect to oil and water. The reported results are of importance for performing realistic reservoir-scale simulations and planning water shut-off procedures