As subsea energy exploration in the oil and gas industry moves into increasingly difficult environments, the number of challenges it presents grows. Used together with traditional engineering techniques, computational fluid dynamic (CFD) analysis provides insight into operational risks and helps identify ways to reduce them, screening alternate solutions quickly without the need for additional full-scale testing, offering valuable knowledge in areas such as erosion modelling, fluids mixing and separation analysis. This article informs on how Apollo's engineers helped design for safe installation and operation of subsea equipment during key stages of a recent multi-well deepwater development using CFD to tackle the challenges at key stages of the development. In particular, the use of CFD in decanting operation and in managing production temperatures at normal operation and at shutdown is highlighted. The development uses pipes for transport and/or injections of fluids. The pipes are constructed onshore and towed out to their position on the seabed. For towing purposes, the pipes are filled with pressurised nitrogen through a high pressure hose (nitrogen decanting). The nitrogen flows into the pipes, expands and cools down (Joule-Thomson effect). To calculate the cooling effect, a transient simulation was carried out, varying the mass flowrate, pressure and temperature according to a 1D-simulator output. The simulation showed that the key material temperatures did not reach the extremes seen in the fluid. Using the analysis, the minimum temperatures of the key material components were derived and a revised strategy based on warming the nitrogen before entering the pipes was used. Once installation is complete, the next set of challenges lies in maintaining a robust flowing production network and maximising recovery. The oil/gas field in consideration will be producing high temperature fluids during its early years, which need a subsea cooling spool. A detailed CFD analysis was used to investigate whether the intended design would provide the necessary cooling. The only appropriate approach was to consider a fully coupled model with both the internal fluid flow in the pipeline and the external seawater currents. The simulation showed how the flow of seawater around the structure influences the temperatures witnessed on the cooling spool. Based on the simulation the length of the cooling spool could be reduced and still achieve the target temperatures. Any production system will be subject to shutdowns where the production fluids are no longer flowing. During a shutdown, the contained fluids will cool to ambient conditions. Some subsea developments can suffer from the presence of hydrates. These ice-like compounds, which generally form under high pressures and low temperatures in the presence of water, are expensive and time consuming to remove. For the development in consideration, an insulation of the subsea production components was chosen so that any remedial action can be carried out before hydrate conditions are reached. To reduce the design iterations required to derive an insulation scheme to meet the cooldown criteria tools were developed. These tools include pre-CFD transient calculations, best practices and automated techniques to develop safer and faster solutions.


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    Titel :

    Subsea CFD


    Beteiligte:
    Ellerton, Paul (Autor:in) / Roberts, Mark (Autor:in)

    Erschienen in:

    TCE - The Chemical Engineer, Rugby ; 877/878(+Bl.) ; 43-45


    Erscheinungsdatum :

    2013


    Format / Umfang :

    3 Seiten, Bilder



    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch





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