EXAMINATION OF PITTING CORROSION IN IRAQI MINERAL WATER

Abstract

It was studied the pitting corrosion in low alloy steel samples by influence of various mining and geological factors of the Iraqi oil field. It is shown that the temperature and chloride content, the ratio of dissolved acid gases CO2 and H2S also affect the development and progress of this process. It was carried out the analysis of voltamperograms of a low alloy steel sample in the simulated reservoir water compositions typical of Iraqi deposits. The analysis of voltamperographs of the sample of low-alloy K55 steel in simulated reservoir compositions at different temperatures and ratios of aggressive CO2 and H2S gases characteristic of Iraqi deposits. It is established that in the presence of hydrogen sulfide in formation water, the potential of free corrosion shifts to the cathode region. Carbon dioxide activates general and pitting corrosion. An active experiment was conducted to study the depth of pitting for the selected steel sample and obtained the second-order regression equation for the dependence of the point corrosion depth on the selected impact factors. The mathematical model was obtained and analyzed for the dependence of the pitting corrosion depth on the selected factors by using the mathematical statistic. The regression model was analyzed, isocontours of influence for different pairs of factors on the depth of pitting corrosion were constructed. The analysis of the obtained model indicates the predominant influence of a factor that reflects the influence of the ratio of corrosive CO2 / H2S gases on the development of local corrosion in formation water. It is shown that there are certain areas with maximum values of the pitting corrosion depth Vp = 91m-6. In natural terms, this equates to a CO2 / H2S ratio of about 17.2.