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Abstract

One of Shell’s deepwater projects has decided to use the cost-saving Single Casing Combo Top-Tension Riser with nitrogen insulation for the Tension Leg Platform (TLP) dry-tree wells to reduce the overall riser cost and TLP payload. However, the thermal performance of such a riser is poorly understood and an accurate prediction model was not available. A conservative thermal-hydraulic design approach would result in redundant requirements for the flow assurance chemicals and unnecessary challenges for the TLP operations. Numerical and experimental work was carried out to better understand and predict the riser thermal performance during startup, normal operation, and shut-in conditions. This paper described the numerical and experimental results. The overall heat transfer coefficients (U-values) from the detailed numerical simulations and experiments were used to derive the effective thermal conductivity (keff) of the nitrogen in the annulus, which includes the effect of all three modes of heat transfer (i.e. conduction, radiation and convention). This effective conductivity for the nitrogen gas was used in a one-dimensional model for the riser. The results of that model give the operator confidence in the system design and operability. The main benefit for the project is less chemical storage weight and space required on the TLP. The experimental and numerical model, with some modifications as required, can be used to optimize performance of riser systems in other projects as well.

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/content/papers/10.3997/2214-4609-pdb.350.iptc17185
2013-03-26
2024-03-29
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.350.iptc17185
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