Effect of Chloride Concentration on the Stress Corrosion Cracking (SCC) of CRA Tubulars and Methods to Enhance SCC Resistance in High-Temperature Environments

Abstract

Abstract Recent failures of corrosion resistant alloy (CRA) production tubing and sand control screens due to stress corrosion cracking have been reported. Investigation of these field failures revealed that calcium chloride completion brine or brine containing calcium chloride was a major component in most failures. Consequently, a growing perception is developing that calcium chloride or even calcium chloride/calcium bromide completion brine should not be considered for use in wells completed with high strength CRA tubulars in high-temperature, high-pressure environments. The impact that completion brine, temperature and acid gas have on the SCC of CRA materials in oilfield environments have been presented in several SPE and NACE publications. However, it becomes necessary to further understand the SCC behavior of high strength CRA materials in brines containing calcium chloride and/or calcium bromide, the most widely used, economical completion brines and packer fluids. The question remains: is there a chloride concentration below which high-strength CRA materials can be safely used in high-temperature well completions. Results for CRA materials tested in calcium chloride, calcium chloride/calcium bromide, and calcium bromide brine for SCC resistance are presented, and the relationship between chloride concentration, type of CRA material, and temperature is discussed. Methods to enhance SCC resistance and minimize the sensitivity of CRA materials to its environment are presented. Practical guidelines for the use of completion brine with CRA metallurgy and chemical treatment is discussed. Results obtained from this study are provided to better design safe, economical completion brine and packer fluids for wells completed with high strength CRA tubulars.