Estudio de trabajo a fatiga en ductos marinos para una unidad flotante de producción, almacenamiento y descarga (FPSO) usando un sistema pasivo de compensación de rolido : estudio del comportamiento mecánico del sistema de risers de un FPSO usando métodos numéricos.

Abstract

The production and transportation of hydrocarbons in the deep water requires the use of a system of underwater pipelines (risers) that transport oil to floating storage and offloading units (FPSO). These risers are subjected to fatigue loading due to the roll motions of the vessel, caused by the cyclical loads of the waves. In the present work, a static analysis of the riser system was carried out, in which pipes that connect from the seabed to a balcony in the FPSO, have a ""J"" shaped configuration. In this configuration, two analysis points were identified: a fixed suspension point and a point in the curvature region, for which the calculation of stresses for the FPSO with and without passive roll compensation system was carried out. For the static study, two analytical models are used: one that considers the pipe as a flexible cable and another that approximates it to a beam in a first section of the riser and cable in the next section. For the cable approach model, without the compensation system, the maximum stress of 29.8 [MPa] is obtained at the point of attachment and at the point of curvature 46.9 [MPa]. With the addition of the compensation system, the values are reduced to 27.4 [MPa] at the fixing point and 43.3 [MPa] at the sag bend region. With these results, it was concluded that the use of a passive compensation system, coupled to the FPSO, reduces the maximum stresses in the risers by 8.5%.