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.
Natural Gas Pipeline Capacity to South Central US To Reach 19 Bcf/D by Year's End
With new projects scheduled to come on line later this year, the region, which mostly comprises states along the US Gulf Coast, will shift from being a source of natural gas supply to a source of growing demand.
McDermott Nets Subsea Tieback Contract for Pemex's Ayatsil Field
The deal covers the installation of a pair of rigid flowlines for the shallow heavy oil field, Pemex’s largest discovery to date. Work is expected to be completed early next year.
Testing of New Pipeline Inspection Device Begins in Bakken
These balls have the potential to alter how pipeline inspections are done, and a consortium of pipeline operators and industry experts in North Dakota is examining just how well this emerging technology can handle the small-diameter pipelines in the area.
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01 August 2018
30 July 2018