Experimental Investigation of the Interference Between Scale Inhibitor and Corrosion Inhibitor in the Context of Selection of Chemical Treatments

Abstract The co-injection of corrosion and scale inhibitors is required for an oilfield in West Africa. The corrosion inhibitor efficiency test is systematically performed in presence of the selected scale inhibitor; however, the reverse is not performed; therefore, the impact of the corrosion inhibitor on the performance of the scale inhibitor is not known. This laboratory study investigates the performance and physical compatibilities of these two chemicals. Combinations of two corrosion inhibitors and two scale inhibitors were examined for sign of incompatibilities. These tests were conducted by diluting the neat chemical into test brines, at the designed dose rates. The brines were heated at temperatures between room temperatures (20°C) and the maximum field temperature (70°C). The two scale inhibitors were evaluated for compatibility with two corrosion inhibitors in dynamic calcium carbonate scale inhibition performance tests. By performing the tests in the presence of gradually decreasing concentrations of scale inhibitor, the minimum inhibitor concentration (MIC) is determined, following which the performance of the scale inhibitors was determined in the presence of the two corrosion inhibitors. The impact on corrosion inhibitors performance from the presence of the scale inhibitors, was determined using linear polarization resistance (LPR) bubble tests. No visible signs of incompatibility were observed between any of the scale and corrosion inhibitors in standard corrosion inhibitor / scale inhibitor compatibility bottle tests. Both scale inhibitors (SI1 and SI2) exhibited a loss of performance in the presence of corrosion inhibitor CI1, which increased minimum inhibitor concentration (MIC) rates determined in dynamic scale tests. Conversely, the corrosion inhibitor CI2 was found to have no impact on the scale inhibitors’ performance. While CL2 showed the better performance of the two corrosion inhibitors in linear polarization resistance (LPR) bubble tests, it did show a slight loss of performance in the presence of either scale inhibitor. Corrosion inhibitor CI1 exhibited poorer performance in corrosion test, with the scale inhibitor having no effect on the corrosion inhibitor’s effectiveness. The laboratory tests showed no couple scale and corrosion inhibitors with no impact on the efficiency both scale and corrosion inhibitors. Although, there are some impacts on the efficiency, these are either minor or small; apart from corrosion inhibitor CI1 which shows a significant increase in the dosage of the scale inhibitor SI2.