Study On Corrosion Inhibition Of Imidazoline Inhibitor In High Temperature And High Pressure CO₂Containing Environments

In recent years, with the oilfield entering into the later development period, the CO2and the moisture contents in crude oil is rising sharply, and the CO2corrosion has become ahuge problem to be solved. The adding of corrosion inhibitor is one kind of anti-corrosionmethods widely used at home and abroad with the advantage of few dosages, low cost andsimple operation. However the corrosion inhibitors are not universal, which need to besimulated and evaluated before serving according to the actual working conditions of thecorresponding field environment, including CO2partial pressure, corrosive medium andproduction rate.Based on the analysis of research status at home and abroad, this article studied thecorrosion of N80and P110in high temperature and high pressure of CO2containingenvironments by using high temperature and high pressure reaction kettle andelectrochemical measurement technology. The study showed that the corrosion rate ofmetals increased with the rising of pressure. Due to the effect of ions in the solution,corrosion rate in liquid phase environment is higher than in gaseous phase environment.Along with the increasing of production rate (oil well producing fluid), the corrosion raterising. When the production rate reached to60m3/d, the corrosion rate was as high as8.41mm/a, which was three times of the static corrosion rate. The study also showed that withthe time lengthening, the corrosion rate tended to be stable after the first drop, and theprotection effect of corrosion products film was remarkable. The surface of corrosionproducts film in liquid phase environment was smooth, and in gaseous phase environmentwas smaller and easier to be removed. The gas phase corrosion products film has a threelayer structure observed by SEM, and the inner layer and the middle layer had a very goodassociative property with the matrix. Using high temperature and high pressure reaction kettle to simulation of CO2partialpressure, corrosive medium and the production rate, and study the corrosion inhibitorinfluence regulations of factors in high temperature and high pressure CO2corrosiveenvironments. The research demonstrated that imidazoline corrosion inhibitor was a kind offast film forming corrosion inhibitor, and time for preparing membrane was4h. Theinhibition efficiency tended to reach to a maximum value with the increasing ofconcentration. The changing of CO2partial pressure had no effect on the inhibitionefficiency with the imidazoline high pressure inhibitors. The inhibition efficiency in liquidphase environment is larger than that in gaseous phase environment, and the inhibitionefficiency also greatly influenced by the corrosive medium and the production rates. Thedifference between inhibition efficiency under production rate of10m3/d and staticinhibition efficiency was not big, when the production rate was60m3/d, the corrosion ratedecreased to90%.The corrosion performance was studied by the polarization curves and AC impedancespectra, and result showed that the imidazoline inhibitor was a mixed corrosion inhibitormainly used for anode inhibition.