This paper discusses the principle and proof of concept of a novel corrosion management tool based on maintaining optimum corrosion inhibitor dose in an inhibited environment. Film-forming corrosion inhibitors typically contain active ionic surfactant molecules which adsorb on surfaces and form a protective barrier against corrosion. Upon saturation of surfaces by the inhibitor, the molecules are found in the aqueous phase as micelles or in the oil phase as reverse micelles. The proposed technique is based on the hypothesis that the presence of these micelles in the water phase could be used to indicate the total surface coverage and therefore the optimum dose.
The technique has been applied in the laboratory simulating an actual inhibited multiphase production system. Fluorescent markers, that are extremely sensitive to micelle presence, have been developed and used during the lab testing. Results were compared to standard laboratory techniques, including interfacial tension (IFT) and particle size analyses (diffraction) in order to determine the efficacy for micelle detection. Corrosion bubble tests were also used to determine any link to inhibitor efficiency.
IFT results showed complex events occurring with increasing inhibitor concentration. The IFT vs. inhibitor concentration curve was non-classical, but suggested micelle formation at around 150ppm. Fluorescence analysis suggested that micelles formed starting at 150ppm dose. Particle size analysis was consistent with micelle presence beyond this concentration.
The analytical comparisons supported the underlying principles of this micelle detection technology. Further development is required to demonstrate the real-time link with corrosion protection, but other studies have already confirmed such correlation. Development of a portable device is underway and will provide an important new tool for proactive corrosion management in the oilfield, as well as a useful laboratory qualification method.