A mini-flowloop was developed to study CO2 corrosion and corrosion/erosion interactions, and to assess the effectiveness of inhibitors under conditions that simulate multi-phase pipelines. The mini-flowloop was used to study the effect of testing time, steel chemistry, velocity, temperature, fluid chemistry, sand and inhibitors on corrosion rates. The measured corrosion rates in inhibited and uninhibited solutions using the mini-flowloop were significantly different from those measured using other methods such as the Greene cell method. The effect of adding 1/2% Cr to the steel did not improve its CO2 corrosion resistance as has been claimed by some suppliers. The presence of oil in a brine solution increased the corrosion rates for both inhibited and uninhibited solutions. The CO2 corrosion rate increased slightly with increasing flow rate suggesting that the corrosion mechanism is partially diffusion controlled. At high flow rates, the presence of sand enhanced corrosion of steel in both uninhibited and inhibited solutions while at low flow rates sand had no effect on corrosion rates in uninhibited solutions, but it had a profound effect on the rates in inhibited solutions. The water soluble inhibitor was effective in controlling uniform corrosion, but failed to control pitting corrosion for tests conducted in 100% water solution. In 90% water-10% oil solution, the effectiveness of the inhibitor decreased and the corrosion rate increased compared to the oil-free case, but pitting was not observed. When a de-emulsifier was added to a solution inhibited by the water soluble inhibitor, corrosion rate increased dramatically. The oil soluble inhibitor was not successful in controlling pitting corrosion at low flow rates or uniform corrosion at high flowrates.

Subject
Test methods, Water, Inhibitor performance, Sand, Corrosion rate, Flow velocity, Solubility, Chemical inhibition, Fluids, Corrosion inhibitors, Steel, Pitting, Oil
Keywords:
Corrosion, pipeline, integrity management, Inhibitors, sand production, CO2
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2009
Association for Materials Protection and Performance (AMPP)
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