SCR Fatigue Mitigation Options for Life Extension

Abstract

Steel Catenary Risers (SCRs) are typically designed to meet requirement for the field life. However, with a possibility for an opportunity for life extension (LE), a remaining life reassessment (RLA) is necessary to be carried out to explore options to extend the life within the SCR integrity framework requirements. It is noted that replacing the whole or specific portion of length of the SCR is not considered as an economically and practically viable option. Several SCR fatigue damage reduction options have been explored for life extension considerations in the industry and the practicality of implementing them to specific field leads to only few choices due to the complexities involved in executing these options. The complexities arise in the execution as the fatigue damage reduction options will require careful re-assessment of floating system performance that includes floater motion, global riser behavior, and mooring system performance. This paper aims to present findings from the fatigue re-assessment as well as the thought process and needed considerations to selecting a mitigation option that is purpose-fit given the value drivers as well as constraints for a typical floater in West Africa deep-water. This is considering that within the West of Africa deep-water fields, this is the first time a practical approach is given to solve the fatigue life extension The fatigue reassessment incorporates as-occurred data parameters that affect global system performance of the SCRs. The fatigue mitigation options considered are repositioning of floater, use of buoyancy modules at midsections of the SCR, and increase in Vortex Induced Vibration (VIV) strakes coverage length. Each of these considered options are analyzed with pros and cons of each option, reviewed to arrive at a purpose fit option. This paper further gives practical insight to how oil and gas industry operators in the Gulf of Guinea region who are considering SCR life extension, can see to integrate methodological steps in seeking solutions to extending field life while maintaining asset integrity. It also highlights the impact of technology and digitalization on asset integrity management. This strategy provides affordability to create earnings from today's energy to fund the energy for future needs.