Analysis of corrosion failure and materials selection for CO₂-H₂S gas well

This paper analyzed the failure of gas wells in Northwest Oilfield and provided corresponding methods to solve the issue. In order to thoroughly investigated the failure factors, methods used in the experiment were material performance testing, SEM, EDS and XRD. Besides, a self-designed HTHP autoclave was used to simulate the real corrosion environment and thereby a new method to choose suitable materials was proposed. The experimental results showed that the chemical composition, metallographic structure, hardness, microstructure and non-metallic inclusion of the failed tubing were all qualified. As a matter of fact, the failure was caused by water-accumulation corrosion which occurred at 6447 m at the bottom of the wellbore, and by water-carrying corrosion occurred at 5086.4m. This paper concluded that the P110ss steel should be selected as tubing in the failed well at a depth of 5086.4m and nickel base alloy steel should be selected at 6447m.