Nanoparticles have potential for multiple applications in the oil and gas industry, ranging from EOR operations to improved drilling fluids and cements, as well as reservoir monitoring and characterization. The two biggest challenges to overcome for nanoparticles in the reservoir are stability at reservoir conditions and retention. Understanding the mechanisms controlling transport and retention in porous media is essential to develop nanoparticles able to successfully traverse the reservoir. A commonly used strategy to stabilize nanoparticles and reduce retention is to functionalize their surface or to coat them with polymers. Although the coatings help stabilize the nanoparticles, retention is still a major challenge preventing field wide applications. Previous studies have shown that increasing the pH of injected water reduces the amount of surfactants (chemically similar to polysaccharides) adsorbed to the rock. This paper presents the results of a study that investigates the possibility of improving the transport properties of a polysaccharide coating (dextran) through a carbonate matrix by altering the pH using an alkaline passivation agent (sodium metaborate). The amount of retention was quantified by fluorescently tagging the dextran and measuring the intensity of fluorescence of the effluents using a portable spectrometer. The intensity of fluorescence of the effluents should be proportional to the amount of dextran being recovered. The results show that the alkali passivation agent reduces retention of the coating by ~16%.

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