High flow velocity can have negative impact on the integrity of the oil and gas production equipment. This negative impact can influence the efficiency of Corrosion Inhibitor (CI). It is well established that the higher the flow velocity, the lower the CI efficiency. Another detrimental effect of flow velocity is the possible occurrence of erosion-corrosion phenomena, where the bare metal will be continuously exposed to the corrosive environment, and thus corroding much faster than in low flow velocity conditions.
The C-factor, as derived from API RP 14E equation, is used as criteria to limit the flow velocity to avoid such severe phenomena. This criterion is dependent on fluid corrosiveness, efficiency of the inhibition and the presence of solid particles. The Company uses a software, an in-house developed tool, to predict and evaluate the risk of erosion-corrosion for different oil and gas production equipment. Typical parameters influencing the corrosiveness of the fluid (water phase composition, CO2 content in the associated gas, pressure, temperature), the production data (GOR, BSW) and the geometry of the equipment are considered when evaluate the likelihood of erosion-corrosion occurrence.
Two case studies are presented, both concerning multiphase subsea production pipelines in service on our offshore assets. As per COMPANY strategy this equipment is periodically inspected via In Line Inspection (ILI) Technology, with the aim of assessing its status. The results of these inspections are analyzed from a corrosion management point of view. Considering real production data and operating conditions, the in-house software was used to evaluate the corrosiveness of the produced fluid and the occurrence of erosion-corrosion phenomena. The predicted corrosion rates are then compared with the ones measured by inspection tools (ILI & non-intrusive thickness monitoring). This analysis is used further on to re-define the corrosion mitigation program.
High flow velocity can have negative impact on the integrity of the oil and gas production equipment. This negative impact can manifest by the reduction of Corrosion Inhibitor (CI) efficiency: the higher the flow velocity, the lower the CI efficiency. The negative impact can also manifest by the occurrence of liquid erosion corrosion phenomena.