08638 Flow Dependancy of Sweet and Sour Corrosion of Carbon Steel Downhole Production Tubing in Khuff Gas Wells

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Product Number: 51300-08638-SG

ISBN: 08638 2008 CP

Author: Ho Jin Choi and Hassan A. Al-Ajwad

Publication Date: 2008

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A series of rotating cage (RC) and jet-impingement (JI) experiments were performed to determine the effect of flow velocity on sweet and sour (SAS) corrosion of API 5CT L80 carbon steel production tubing under simulated Khuff gas well conditions. As observed in a field SAS corrosion study of the carbon steel, two distinctively different corrosion mechanisms were replicated: SAS general and pitting corrosion. Both corrosion mechanisms appear to be flow-dependent. SAS general corrosion rate was relatively low but SAS pitting corrosion rate can be an order of magnitude greater than that of SAS general corrosion. In other words, the general corrosion is not a threat in using carbon steel production tubing but the pitting corrosion is, assuming a five year work-over (WO) interval is acceptable and cost-effective. Other parameters that control SAS corrosion was exposure time, H2S/CO2 ratio, chloride concentration, temperature, etc. It was noted that SAS pitting corrosion initiated under a special combination of high wall shear stress and high chloride concentration regardless of H2S/CO2 ratio but its propagation mechanism was still well-understood.