SCC-CO2 Failure Mode: Literature Review and Available Technologies Used to Inspect and Access the Integrity of the Flexible Pipes

Abstract In 2017, after a failure of a flexible riser operating in an environment with high level of CO2, a new failure mode of the flexible pipes was reported: Stress Corrosion Cracking induced by CO2(SCC-CO2). This issue was not considered in the design and manufacturing standards of these equipment. In this context, this paper covers a literature of SCC-CO2 phenomenon. Moreover, the impacts on the flexible pipes due to this failure mode are discussed. Lastly, this research focuses on the current technologies and tools used to inspect and access the integrity of the pipes used on gas injection and production lines. The paper is written based on detailed review of the literature. A set of relevant keywords were used on peer-reviewed journal articles and conference papers mainly available in the OnePetro database. Some recognized books, technical specifications and PhD thesis were also consulted. The papers included in this literature review were selected based on four steps: identification, screening, eligibility and inclusion (Moher et al., 2009). This methodology allowed to find out what is the current state of the art about the topics covered in this study. This detailed review of literature revealed that after the issue reported in 2017, the industry invested in the research of the SCC-CO2 phenomenon. Many studies were conducted in order to investigate what are the main factors that triggers this failure mode on the flexible pipes used for the production and gas injection in the deep-water and ultra-deep-water fields with high levels of contaminants and harsh metaocean conditions. Then, different technologies and tools were developed to inspect the flexible pipes. Operators can use this data to estimate the remaining service life of the lines. There are proven tools that can inspect the gas injection pipes using different non-destructive techniques. However, there is still a gap on the inspections of the annular region of the production flexible pipes. This happens due to the limitation of reading through the thermal insulation layer contained on them. This is very critical because the inspection of the pipe annulus detects if it is dry or flooded. This information is vital to assess the integrity of the structural armors of the flexible pipes.