Since its first floating production application in 1994 to Shell's Auger TLP in the Gulf of Mexico, steel catenary riser (SCR) technology has been a rapidly evolving area of riser engineering. With recent widespread application to production service, deeper water, higher motion floaters and more corrosive fluids, safety-critical production and export SCRs are operating under increasingly challenging design conditions.
To date, no widely-accepted systematic approach has been developed for the assessment of risk for these systems and the development of appropriate integrity management strategy based on that risk. Risk-based integrity management of SCRs has lagged behind such approaches developed for other safetycritical assets like pipelines and flexible risers. Recently reported failures of some SCR components (flexible joints and stress joints) has provided increased incentive for ensuring that systematic integrity management programs, combined with effective monitoring and inspection methods, exist that are capable of prevention or early detection of integrity problems with such systems.
This paper describes the background and scope of an industry-wide SCR integrity Management (SCRIM) joint industry project (JIP) which has developed a systematic riskbased approach to the management of SCR integrity. The paper illustrates how an approach to SCR integrity can be developed which is consistent with the approach taken to other safety critical systems when it comes to assessing the need for integrity management measures.
The requirement for risk-based integrity management of any asset is related to the inherent risk of loss of integrity during its service life. Over the first ten years of their application to floating production service, SCRs have mostly been used for gas and oil export service to low motion vessels in relatively benign sea conditions. In recent years, however, the increased focus on controlling risk and managing riser integrity has been driven by several issues which highlight the increasing technical challenges associated with SCRs and the benefits of through-life integrity management:
Increasing application of SCRs as a riser solution. Compared to relatively few SCRs in service at the turn of the millennium, close to 200 SCRs are now either installed or are at the planning stages in projects worldwide, in water depths up to 8,000 ft (Independence Hub, Gulf of Mexico), driven largely by their increased application to production as well as export service.
Use of SCRs for higher motion vessels: SCRs were first used in the early 1990s for TLP applications (Shell Auger and Mars, Gulf of Mexico). Subsequently, they have been used for higher motion floaters such as semi-submersibles (Petrobras P-18, P36, Brazil, and Atlantis, Na Kika and Thunderhorse, Gulf of Mexico) and FPSOs (Bonga, Erha, Akpo in West Africa).