Top of Line Corrosion (TLC) Behaviour with Presence of Gas Condensate in CO2 Wet Gas Pipeline

Abstract

AbstractTop of line corrosion (TLC) in CO2 wet gas pipeline is a major threat to oil and gas industry, where difference in temperature of internal pipeline and outside environment leads to condensation of water in a stratified flow regime. This condensed water is corrosive to the pipelines’ surface because it contains organic acids and dissolved acidic gases such as CO2 and H2S. In oil and gas field, gas condensate is usually present in the pipeline. However, only gas condensate-free TLC systems were usually studied. This condensable hydrocarbon may affect condensation process as it is immiscible with water which leads to different wettability on the pipeline surface. In this work, TLC testing with and without gas condensate was carried out to study the effect of gas condensate on the water condensation rate (WCR) and the TLC rate. The experimental work was carried out in a 2.0 L TLC testing unit using API 5L X65 carbon steel coupons for 7 days. The corrosion rate was calculated using the weight loss method in accordance to ASTM G1-03, surface morphology analysis by Scanning Electron Microscopy (SEM) and the pitting was observed by using the Infinite Focus Microscope (IFM) in accordance to ASTM 46-94. The presence of gas condensate in the system led to a 62% lower WCR compared to that of gas condensate-free system at the same temperature difference between gas and steel (∆T, °C). TLC rate was found to be higher in gas condensate-free system with a difference of 33%. Overall, the presence of gas condensate has reduced the WCR which then reduced the TLC rate.KeywordsTop of line corrosionGas condensateCorrosion rate