Life Extension of the Risers Used for the Hoover DDCV in Gulf of Mexico

Abstract

This paper investigates life extension of the risers used for the Hoover DDCV (a classical Spar) in GoM, based on the latest technology and monitored data. Deepwater development in Gulf of Mexico (GoM) started about two decades ago. It is the time to evaluate the global integrity of the riser systems and explore the possibility of life extension in a structured and systematic way. A Deep Draft Caisson Vessel (DDCV), has been keeping up its class services for the past 17 years since it was installed in 2000. It was expected to extend the riser design life by 10 more years. This paper showed the life extension verification process starting from the initial planning, reviewing of the original design document, gathering and analyzing production and offshore measured data and finally to offshore focused underwater inspection. It introduces the methodology to assess the integrity of Steel Catenary Risers (SCRs) and Top Tensioned Risers (TTRs) used for the DDCV. An independent global performance was analyzed by utilizing latest environmental data, as-built information, measured VIM motion data and the latest analytical tools. It computes the riser global performance including dynamic strength and fatigue with the contributions from wave fatigue, VIM and VIV. The factored riser fatigue life is provided with the original safety factors to meet the intended 10 more years of service life.