The paper covers the study results of corrosion activity within the process and subsea pipelines, equipment for gathering, transport and treatment of oil-gas-fluid mixture and associated gas at Vietsovpetro offshore facilities. The analyse results, obtained during 2015-2020, showed that the associated gas incoming to compressor stations contains the following concentrations of components: СО2 up to 1.25%, H2S up to 50 mg/l, Н2O up to 2.0 g/m3, and may have the high corrosive activity. Based on the results of corrosion monitoring in the subsea pipelines of low-pressure gas and gaslift at the compressor stations, it may be concluded that the actual corrosion rates are low (0.018-0.042 mm/year). However, the process pipelines and compressor platforms’ equipment undergo higher internal corrosion due to higher operation temperatures and humidity of the treated associated gas. Corrosion rate in the process equipment may reach 0.35 mm/year, requiring additional corrosion control actions. Corrosion activity of well stream within the gathering, transportation and treatment system of oil and production water at the at Vietsovpetro offshore facilities depends on the presence of associated water (60% in average), leading to the increased probability of corrosion processes within the oil-gas-fluid mixtures pipelines by a higher content of single water phase. According to the results of direct measuring in the associated water, the corrosion rate for carbon steel is 0.04-0.22 mm/year. Active local corrosion is observed in the pipelines of production water treatment modules at technology platforms prior to sea dumping. Corrosion rate for the water treatment equipment (degasser, electrohydrator, sludge tanks, caissons) exceeds 1.5 mm/year and depends on the presence of dissolved oxygen during the technological process of removing the residual oil from the reservoir water prior to discharge into the sea. To control the corrosion activity in the pipelines and equipment at the offshore facilities at Vietsovpetro, the following measures have been successfully applied: corrosion inhibitor injection, replacement of carbon steel to corrosion-resistant materials, deployment of corrosion monitoring system.
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