Study and Practice for Corrosion Prevention in Water Processing System in Iraq Ah Oilfield

Abstract

Water processing system in Iraq Ah Oilfield suffered a lot from corrosion affects like pipeline, tank, flange, valve leakage from 2015 to 2018. That caused both loss and pollution over 100 times one year. In order to solve this problem, phenomenon was checked and statistics, observation and laboratory test were carried out. After researching all the possible factors like Cl⁻¹, pH, Fe²⁺, DO, SRB, CO⁻², H₂S, fluid flow velocity, suspended pollutant combined with laboratory results, it is confirmed H₂S and SRB are the two main causes of pitting corrosion. The mechanism is that H2S (over 100 ppm) in produced water reacts with Fe, creating FeS scale. SRB accelerates the corrosion between FeS scale and steel. The maximum pitting corrosion rate can reach to 0.7 mm/y.

Based on the analysis, gas stripping device was developed, which reduced the H2S concentration from about 140 ppm to about 50 ppm. Together with bactericide, FRP upgrading and cathode protection, the leakage caused by corrosion decreased about 70% one year. It is of great sense to find out the root cause and according control ways of corrosion from so many effecting factors. Considering the high similarity of producing reservoir and produced water in most oil fields in Iraq, as the first one to imply water injection developed oil field, corrosion prevention study and practice is very meaningful for the others. Ah Oilfield is also established as corrosion prevention and treatment example by Ministry of Oil of Iraq.