Deepwater HPHT pipelines are generally susceptible to significant end expansion and axial walking. Pipeline walking can cause cumulative axial displacement of the entire pipeline, which can induce damage at termination units, expansion spools and riser tie-ins. The rate of walking depends not only on the temperature profiles, but also on the magnitude of axial resistance, the mobilization distance and the seabed topography.
In this paper, Filip Van den Abeele, Jean-Christophe Ballard and Charles de Brier from Fugro GeoConsulting (Belgium) present parametric FE analyses performed with SAGE Profile. The results indicate that the powerful pipe-soil interaction library of SAGE Profile is capable of accurately capturing the phenomenon of axial walking
More sophisticated axial pipe-soil responses, derived from the SMARTPIPE measurements, were implemented to assess the impact on the predicted and expansion walking rate. The axial pipe-soil interaction was captured by a tri-linear soil spring, and the effects of mobilization distance, peak friction factor and residual friction factor were evaluated by performing sensitivity analyses. Moreover, the tri-linear soil spring in SAGE Profile allows distinguishing between the initial (first loading) stiffness, the unloading stiffness and the reloading stiffness.
>> Read more – 2013
Vortex induced vibration is a major cause of fatigue failure in submarine oil and gas pipelines and steel catenary risers. In their paper “Fatigue Analysis of Free Spanning Pipelines Subjected to Vortex Induced Vibrations”, dr. ir. Filip Van den Abeele and ir. Frédérique Boël, present a case study from the offshore industry, in association with Shell Exploration & Production. For a deepwater pipeline in the Gulf of Mexico, the remaining fatigue capacity of a long slender span subjected to VIV was analyzed using the DNV-RP-F105 span check offered by SAGE Profile. This powerful capability provides a quick and easy tool to evaluate the severity of free spans for a given pipeline route, and hence can save a tremendous amount of time and money associated with seabed rectification.
In this paper, an integrated numerical framework is presented to predict and identify free spans that may be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). Sensitivity analyses are performed to study the influence of the seabed conditions, where special emphasis is devoted on the selection of pipe soil interaction parameters.
The paper has been presented at the International Conference on Offshore Mechanics and Arctic Engineering (OMAE 2013).
>> Read more – 2013
The December 2012 issue of the Journal of Pipeline Engineering presents an overview of numerical modelling and analysis for offshore pipeline design, installation, and operation. SAGE Profile 3D is used to demonstrate the added value of numerical modelling as a design aid and decision tool throughout the entire life of an offshore pipeline.
In their article on ‘Numerical Modelling and Analysis for Offshore Pipeline Design, Installation and Operation’, SAGE Profile experts dr. ir. Filip Van den Abeele and ir. Raphaël Denis present case studies on pipe-soil interaction, free span evaluation, lateral buckling, upheaval buckling and pipeline walking. This comprehensive review demonstrates the versatility of finite element methods as a powerful support tool in offshore pipeline design.
>> Read more – 2012
Daniel Cameiro and Adriano Castelo of Bureau Veritas explain how they use SAGE Profile 3D in their paper “Thermo-mechanical analyses of HP/HT pipelines with sliding foundation end structures”.
Non-buried subsea pipelines subjected to high internal pressures and high operational temperatures (HP/HT) might experience significant axial expansion. If this movement is restrained by an end structure, considerable loads can be imposed to the system. Sliding foundations have been used to minimize this effect, allowing free end displacement despite the equipment. However, thermo-mechanical behavior of HP/HT pipelines interacts with the end restrains in a complex manner. Axial displacements can accumulate over the operational cycles, in the phenomenon known as “pipeline walking”. If the sliding foundation design does not account for these accumulated displacements, axial loads (not considered in the pipeline design) might be imposed. As a result, the overall thermo-mechanical behavior in terms of lateral buckling and walking can change significantly.
This paper presents the results of finite element analyses performed to verify the importance of this interaction between the thermo-mechanical loads and the non-linear end restrain. The analyses were performed using highly non-linear tri-dimensional finite element models considering pipe-soil interaction with full 3D seabed bathymetry and load history maintained from pipe lay to operational cycles. The limited sliding range was imposed to the model ends. The results show that the pipeline global behavior after a few operational cycles is significantly different from the foreseen for the initial condition.
>> Read more – 2010
Offshore pipelines laid on the seabed are exposed to hydrodynamic and cyclic operational loading. As a result, they may experience on-bottom instabilities, walking and lateral buckling. Finite element simulations are required at different stages of the pipeline design to check the different loading cases. Pipeline design is dependent on accurate modelling of axial and lateral soil resistances (Bruton, 2008). The pipe-soil interaction of surface laid pipelines is still too often modelled using single frictional factors in the axial and lateral directions. These assumptions are too simplistic, especially in soft deepwater clay. Improved modelling of the pipe-soil interaction can help significantly reduce costs through optimising pipeline design.
Based on recent research, these simple models were improved and implemented in a finite element software program for pipeline analysis, to better simulate the pipe-soil interaction of surface laid pipelines and to more accurately simulate full routes. In this paper, the main features of the soil models are explained. There are several improvements. A more recent pipe-soil vertical reaction law that models plastic unloading is built into the program. It considers lay and dynamic installation effects to compute a more representative pipeline embedment. Axial and lateral resistance is now linked to pipeline embedment. Finally, peak-residual axial and lateral reaction laws are implemented.
>> Read more – 2009