Abstract

One key technology for Deep-Sea Mining is the riser system. The riser is already a field-proven technology in the Petroleum Industry. However, several differences exist between a petroleum production riser and a riser for Deep-Sea Mining, mainly related to the internal flow. The ore-slurry has a larger density than the hydrocarbons and shall be pumped with a much higher flowrate.

The current software tools for riser’s dynamic analysis may include the internal fluid hydrostatic pressure and the centrifugal and Coriolis forces imposed by the bent pipe’s internal flow. However, the internal pressure drop is not calculated. The internal pressure alters the pipe’s effective tension and can alter the pipe’s bending moment changing its mechanical behavior.

This article describes a computational script’s development to run embedded in a commercial software for riser’s dynamic analysis. Our script calculates the internal viscous pressure drop along with the jumper. This pressure is then converted into wall axial tension (buckling) and imposed on each node of the jumper’s numerical model.

Each simulation case was calculated twice with and without the internal flow viscous pressure drop. The comparison with experimental data revealed that the jumper’s average position has a good agreement among all cases. However, the amplitude caused by the top oscillation showed some discrepancies. Experimental data has the highest amplitude in the horizontal direction, while the simulation without viscous pressure calculation had the smallest. The simulation with our embedded script had intermediary amplitude in the horizontal direction. The vertical direction amplitudes have the same behavior for all cases, but the experimental data showed the highest amplitude.

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