As offshore activities move into deep water, there is a growing interest in the use of composite production risers to replace steel risers. There are a number of potential benefits using composite risers on floating production systems in deep water. The most significant advantage is in the reduction in weight and thus payload for floating production systems. Other potential advantages include excellent fatigue, thermal and damping properties and high corrosion resistance.
Composite risers have not been used in the Gulf of Mexico to date. The Minerals Management Service’s Deepwater Operating Plan (DWOP) requires that new technology introduced in a deepwater development project must be shown to be as safe as existing technology. This project was undertaken to examine the relative risks of composite and steel production risers. A Comparative Risk Analysis was completed for a steel and a composite production riser system for a deepwater floating production system operating in the Gulf of Mexico. The risks for a composite production riser and a steel riser that both had the same functional requirements and service life were compared to demonstrate the relative safety of the composite and steel riser.
The steel riser analyzed in this study was an example riser configuration developed for this study. It was based on conventional and proven technology and design practices that have provided numerous deepwater risers that have been successfully used in many Gulf of Mexico projects, and had no special attributes specifically that were included for the purposes of this study.
A similar background of experience and well-established design practices are not available for composite production risers. Therefore a composite riser had to be “configured” for the purposes of this project. The configuration sought to include all the design consideration needed to meet the functional requirements and service life, but only in sufficient detail for the comparative risk study. The resulting composite riser configuration should not be taken as a final design. Rather we believe that it represents a realistic configuration that could be taken to a successful final design and application, and is detailed enough to evaluate the major risks for a composite production system. Details of the description and analyses of the CPR will be highlighted in this document.
The results of this study indicate that a composite production riser can be designed to be as safe as a steel production riser for deepwater applications in the Gulf of Mexico.
This report presents a summary of the results of this study. More detailed information and results are available in Appendices A, B, and C to this report.
Appendix A is the report Global Riser Analysis for the Composite and Steel Production Riser CRA by Charles Miller of Stress Engineering Services. The report provides a description of the steel and composite risers and summarizes their global analyses of both risers in design and fatigue seastates, their detailed design and fatigue studies of the steel riser.
Appendix B is the report Comparative Risk Analysis of Composite and Steel Production Risers: Composite Riser Response Assessment by Won Kim and Dr. Ozden Ochoa, his PhD advisor, of Texas A&M University, which focuses on the composite riser. It includes a more detailed description of that riser and summarizes the various analyses completed assess the performance and failure modes of the composite riser.
Appendix C is the MS thesis Risk Analysis of Steel Production Risers for Deepwater Offshore Facilities by Anubhav Jain (his MS advisor Dr. Robert Gilbert) of The University of Texas at Austin. That report includes the risk framework developed for this study and an example application to the steel riser.