Understanding and Quantifying Corrosion of L80 Carbon Steel in Sour Environments

Abstract

Abstract The prediction of carbon steel corrosion in sour acid gas environment is more challenging than that in sweet acid gas environments, because in the former environments various iron sulfide scales can form that result in different corrosion mechanisms. A unique approach was developed to study the complex sour acid gas corrosion behavior, which combined the use of long-term corrosion testing data, facility life prediction data obtained from extreme value statistics method (EVS), and validation with long-term field caliper data. This approach was used to evaluate the applicability of carbon steel for downhole tubing in sour acid gas environments, in order to achieve optimum capital expenditure and long-term facilities integrity. The effects of three key parameters on L80 carbon steel tubing corrosion were investigated. These parameters were H2S concentration, chloride level, and test duration. Laboratory data combining EVS method were used to predict the tubing life, which were then compared with field caliper inspection data. This comparison showed that predictions based on long-duration laboratory data were consistent with the available field caliper data. It also indicated that field caliper inspection data provided reliable information for tubing life predictions, which complemented mechanistic understanding from laboratory studies.