Oilfield Environment-Induced Stress Corrosion Cracking of CRAs in Completion Brines

Abstract

Abstract Failures, due to stress corrosion cracking (SCC), of corrosion resistant alloy (CRA) production tubing or sand control screens have been reported in recent years. Increased use of CRA materials for downhole applications is the result of stringent requirements for high-temperature high-pressure and sweet/sour production environments, and competitive cost and availability of CRAs. Most SCC failures are related to the use of high strength CRA materials. Field observations and laboratory tests indicated that SCC of high strength CRAs was strongly related to the demanding environment in which the CRA tubulars were exposed. Oilfield environments such as the properties of associated fluids, temperatures, acid gases, types of CRA, and mechanical demands, to name a few, have been found to have a significant impact on the SCC process. This paper presents comprehensive results from SCC evaluations of various CRA materials under different oilfield environments. The impact on SCC of different types of CRA materials for a range of temperatures, completion fluid compositions and additives was studied. SCC was also evaluated under various CO2 and CO2/H2S pressures in order to determine the stress corrosion cracking potential of CRAs. Discussion of the best practices for field applications, including on-site monitoring, control of pH and oxygen contamination, as well as other chemical additives, will be presented. These results and discussion are significant in identifying environmental factors directly related to oilfield SCC failures and in selecting best completion practices.