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  1. Opus
22 November 2010

Opus Conducts Pioneering Study for Evaluating the Influence on Separation from FPSO Motion

Liquid ‘sloshing’ inside separators and other process vessels on floating oil production facilities can cause serious operational constraints and unexpected loads on equipment if the analysis and designs are not appropriate.

Opus has completed a significant number of separator upgrades on floating production facilities in order to improve throughput and solve performance difficulties due to the motion of the sea.

To further advance our competency and provide clients with a high degree of confidence, Opus has recently completed a successful development project in collaboration with its business partner CD-adapco.

Both physical modelling techniques (VDM) and mathematical modelling techniques (CFD) are used by Opus to undertake upgrade work for oil companies. The objective of the project was to corroborate and verify the results from computational fluid dynamics (CFD) and visual dynamic modelling (VDM), for studying the influence of motion on the fluids within a separator, operating on FPSOs.

An actual upgrade application for a first stage production separator on a North Sea FPSO was used as the subject. The troubleshooting and upgrade scope for the separator included VDM sloshing analysis.

Opus developed a mutual scope of work with CD-adapco to develop the best methodology to analyse the sloshing within the separator using CD-adapco’s versatile STAR-CCM+ CFD software. Comparisons were then made between results from the visual dynamic modelling and the CFD analysis.

The project encompassed a 3D multi-phase CFD analysis of the separator at the same scale and geometry of the model separator so that direct comparisons could be made between the CFD and the VDM results through the creation of real-time animations.

The pioneering nature of this project was to consider verification between two scaled models of the actual separator; with the objective of not only obtaining a good correlation between the motion behaviour of the liquid / gas interface, but also achieving correlation with the simulated liquid flowing through the separator concurrent with the real flow conditions in the actual vessel.

The extensive elements of the computational model provided challenges to an already complex problem solving exercise. However, with the combined knowledge and experience of Opus and CD-adapco personnel, these challenges were overcome.

The final results have provided an excellent correlation between the CFD and the VDM techniques not only in terms of the interface tracking but also in terms of the flow field behaviour within the liquid pool.

Drawing on the benefits of each method, Opus is able to provide a unique verification tool that is second to none for process vessel design for floating production facilities.

Our clients will gain from the high levels of certainty that proposed separator designs and upgrade modifications will have in terms of added value to their production throughput and reliability.

Offshore Product Optimisation
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