1. Study on torsional response and ultimate loading of unbonded flexible risers under corrosion defects.
- Author
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Lei, Qinglong, Hou, Zhi, Zhu, Xiaohua, and Chen, Chenyang
- Subjects
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TORSIONAL load , *TORSIONAL stiffness , *FAILURE mode & effects analysis , *TORSION , *CARBON dioxide , *PETROLEUM industry - Abstract
During the process of deep-sea oil and gas exploitation, unbonded flexible risers (UFRs) are corroded by CO 2 and other media over long periods of time, which causes serious damage to the tensile armor layers and threatens the safety of the UFRs in service. To study the effects of torsional response, ultimate loading, and failure mode on UFRs after corrosion, and to reveal the torsional failure mechanism of the UFR while considering corrosion defects, an 8-layer UFR torsional response model is established in this paper. Local bending of the UFR and lateral buckling failure of the inner tensile armor layer occur under counterclockwise ultimate torsion, whereas strength failure of the inner tensile armor layer occurs under clockwise torsion. When the degree of corrosion is 0.4 mm, the counterclockwise torsional stiffness of thickness corrosion, width corrosion, and combined corrosion decreases by 27.6%, 10.8%, and 28.4%, and the ultimate loading of counterclockwise torsion for thickness corrosion, width corrosion, and combined corrosion decreases by 37%, 13.4%, and 39.3%, respectively. Therefore, the influence of thickness corrosion and combined corrosion on the torsional response of UFRs is worthy of further attention. • Established a theoretical and numerical model for unbonded flexible risers, and compared and verified the correctness of the model. • Studied the influence of corrosion of the tensile armor layer on the torsional response of unbonded flexible risers. • Revealed the ultimate torsional failure mechanism of unbonded flexible risers. • Restored the lateral buckling failure mode of unbonded flexible risers. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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