Dynamic Flexible Riser Ancillary Equipment—North Sea Asset Integrity Management Experience and Lessons Learned

Abstract

Dynamic flexible risers are complex engineered systems, which provide a connection between topside (normally floating) facilities and subsea pipeline infrastructure on offshore oilfields. Such systems require the use of ancillary equipment to ensure the riser’s correct configuration is maintained throughout the service life. Industry experience shows that the integrity management of riser ancillary equipment is not always comprehensive, and failure of such equipment is one of the causes of premature removal of flexible risers from service. This article presents some case studies from the operational experience of dynamic flexible risers by an operator in the UK North Sea covering a period of approximately 20 years. The case studies look at the anomalies identified in service by general visual inspection (GVI) using a remotely operated vehicle (ROV) and the lessons learned. Some of the anomalies, had they not been identified and addressed promptly, could have resulted in costly repairs, which demonstrates the importance of inspecting the ancillary equipment of flexible risers as a part of the riser integrity management strategy. The challenges associated with integrity management of ancillary equipment of dynamic flexible risers are also discussed. The case studies presented in this article demonstrate that ROV GVI is an effective method for identifying installation and in-service anomalies related to flexible riser ancillary equipment. The purpose of this article is to share lessons learned with the wider offshore oil and gas community. It is also believed that the information presented in this article may provide useful information to other users of dynamic flexible riser systems when developing and/or implementing their subsea pipelines integrity management programs.