Trenching effects on structural safety assessment of integrated riser/semisubmersible in cohesive soil

Elosta, Hany; Huang, Shan; Incecik, Atilla

doi:10.1016/j.engstruct.2014.07.029

Cited by 17 publications

(4 citation statements)

References 19 publications

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“…Yang and Xiao [17] revealed the non-linear dynamic responses of a top-tensioned riser (TTR) under the combined action of multi-frequency parameter excitation and vortex excitation. Elosta et al [18] studied the influence of a submarine trench and geotechnical parameters on the Most of the early studies on steel catenary risers were based on experiments and can be divided into two categories, which are full-scale experiments and small-scale experiments. Furthermore, 2H Offshore Engineering maybe was the first company to investigate the interactions between the soil and pipes in the TDZ of a steel catenary riser with a full-scale model experiment [5].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Research on the Dynamic Response of a Steel Catenary Riser in the Touchdown Zone under Pigging Conditions

Zhu

Wang

et al. 2023

Energies

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A periodic pigging operation performed to clean off sediment and provide operators with detailed health information for a pipeline is mandatorily required. The research on pigging-induced issues for the steel catenary riser (SCR), one of the key parts in offshore hydrocarbon recovery pipelines between the floating production system and the seabed, has been scarce until now. As a result, there is an urgent need for theories to guide the pigging operation to ensure safe pigging is achieved in deepwater risers. In this paper, a study aiming to determine the effects of the pigging impact load and the pigging-induced slugging load on the dynamic response of the riser is reported. A SCR pigging model was established and proposed based on the finite element analysis (FEA) method. The stress distribution and displacement of the SCR were investigated under the pigging conditions, with the consideration of the effects of waves, currents, and floating platform movements. It was found that the pigging load has large effects on the stress and displacement of the touchdown zone (TDZ), especially the touchdown point (TDP). The displacement of the TDZ in the Y (vertical) direction is more significant than that in the X (horizontal) direction under pigging conditions, and the maximum displacement of the TDZ in the Y direction is proportional to the weight of the pig, as well as the length of the pigging-induced slugging.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Research on the Dynamic Response of a Steel Catenary Riser in the Touchdown Zone under Pigging Conditions

Zhu

Wang

et al. 2023

Energies

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“…Fatigue life calculations are strongly influenced by the seabed strength and stiffness at the TDZ (Kimiaei et al 2010;Li & Low 2012;Queau et al 2013;Elosta et al 2013;Elosta et al 2014).…”

Section: Introductionmentioning

confidence: 99%

An effective stress analysis for predicting the evolution of SCR–seabed stiffness accounting for consolidation

2020

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Steel catenary risers (SCRs) are an efficient solution to transfer hydrocarbons from deep-water seabeds to floating facilities. SCR design requires an assessment of the fatigue life in the touchdown zone, where the riser interacts with the seabed, which relies on reliable estimates of the SCR-seabed stiffness over the design life. Current models for SCR-seabed stiffness consider only undrained conditions, neglecting the development and dissipation of excess pore pressures that occur over the life of the SCR. This consolidation process alters the seabed strength and consequently the SCR-seabed stiffness. This paper summarises experimental data that shows that long-term cyclic vertical motion of an SCR at the touchdown zone leads to a reduction in seabed strength due to remoulding and water entrainment, but that this degradation is eclipsed by the regain in soil strength during consolidation. The main focus of this paper is on prediction of the temporal changes in seabed strength and stiffness due to long-term cyclic shearing and consolidation, to support calculations of SCRseabed interaction. The predictions are obtained using a framework that considers the change in effective stress and hence soil strength using critical state concepts, and that considers the soil domain as a one-dimensional column of elements. The merit of the model is assessed via simulations of SCR centrifuge model tests with over 3,000 cycles of repeated undrained vertical cycles in normally consolidated kaolin clay. Comparisons of the simulated and measured

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“…This model was in detail verified by using a pipe test in Kaolin (Aubeny et al, 2008b). Elosta et al (2013Elosta et al ( , 2014 applied Orcaflex to investigate the effect of the seabed lateral stiffness on the trench development and the fatigue damage near TDP. Shiri (2014a) implemented the nonlinear hysteretic seabed model in ABAQUS based on UEL to study the response of SCR near TDP.…”

Section: Introductionmentioning

confidence: 99%

Study of Seabed Trench Induced by Steel Catenary Riser and Seabed Interaction

Wang

Low

2016

Volume 5: Pipelines, Risers, and Subsea Systems

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Seabed trench profile has significant effect on the fatigue damage of steel catenary riser near touchdown point. This study briefly demonstrates an approach in literature to determine the seabed trench induced by wave frequency response based on the cubic polynomial model. In this approach, a criterion for the matching between catenary riser and seabed trench is proposed, which is an optimization problem, and needs iterative static analysis of catenary riser. Based on the criterion, the sensitivity of the trench length and position to three parameters is parametrically studied: riser mass per unit length, ratio of horizontal span to vertical span of catenary part, trench depth. The obtained data are employed to fit the equations of trench length and position, which is taken as surrogate model since the iterative static analysis is very complicated. For completeness, the validation against data obtained from hysteretic seabed model is also illustrated. Based on the surrogate model, this study investigates the effect of trench depth on the fatigue damage near touchdown and the effect of the low frequency response on the seabed trench, and some useful conclusions are obtained.

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Trenching effects on structural safety assessment of integrated riser/semisubmersible in cohesive soil

Cited by 17 publications

References 19 publications

Research on the Dynamic Response of a Steel Catenary Riser in the Touchdown Zone under Pigging Conditions

Research on the Dynamic Response of a Steel Catenary Riser in the Touchdown Zone under Pigging Conditions

An effective stress analysis for predicting the evolution of SCR–seabed stiffness accounting for consolidation

Study of Seabed Trench Induced by Steel Catenary Riser and Seabed Interaction

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