Dynamic Plastic Deformation of Deepwater Steel Catenary Risers Under Extreme Cyclic Compressive Loading
Steel catenary risers (SCRs) on a large-heave-motion vessel are susceptible to compression in the riser touchdown zone (TDZ). Dynamic compression can lead to overstress under extreme or abnormal weather conditions. The response of an SCR under compression is highly nonlinear and sensitive to various factors. However, the current available industry design codes and practices do not provide a clear guidance to address the acceptability of compression, overstress, and the resulting plastic strains. In addition, the current analysis method used in industry common practice cannot capture accurately the nonlinear behavior of an SCR involving accumulated plastic deformation, hysteresis effects, and local buckling.
In this paper, a finite-element-analysis modeling method that uses combined beam and solid elements is presented. This method enables simulation of large plastic deformation, pipe ovality, and local pipe buckling in the TDZ of a deepwater SCR. The model is developed with Abaqus (Dassault Systèmes 2009). The SCR non- linear response is examined through dynamic analysis of a deep- water SCR that is hung from a semisubmersible. The key analysis results are compared with a nonlinear beam-element model. More- over, dynamic-ratcheting analysis under multiple plastic-strain cycles by use of the proposed solid-riser model is conducted to understand the plastic-strain accumulation and to check the acceptability of the survival response of a deepwater SCR under a series of severe hurricanes in its service life.
This paper presents the methodology for evaluating the compression and plastic deformation that could be experienced by deepwater SCRs, including the modeling approach, analysis results, possible failure modes, and conclusions. The impact of the study findings on the robustness and suitability of SCRs for deepwater application is discussed.
Phillips 66 Forms JVs To Boost Takeaway Capacity from Bakken and Permian
Phillips 66 and partners in two separate joint ventures are building the Red Oak and the Liberty pipeline systems to deliver a total of approximately 750,000 BOPD to the US Gulf Coast with startup of service in early 2021.
Cactus II Pipeline To Start Partial Service in the Permian by Year End
Approximately 90% of construction work has been completed on the pipeline, which is expected to transport up to 670,000 BOPD from the Permian Basin to the US Gulf Coast. Cactus II is one of several pipelines aimed at alleviating takeaway concerns in the Permian.
Can Robots Improve Above-Water Riser Inspections?
The criticality of above-water riser hull piping requires frequent inspections. Traditional manual inspection methods present safety and efficiency concerns, but work is being done to see if robotic technologies—such as drones and crawlers—can do the job as good as, or even better, than humans.
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04 June 2019
05 June 2019