Comparative Analysis of Umbilical Pull-in through J-tubes by Detailed Models and Simplified Methods

Abstract

Design and installation of offshore structures and subsea pipelines requires knowledge about loads that will affect the equipment during the installation process and estimates of the load effects during the lifetime of the structures. For design of subsea pipelines the connection to offshore structures is an important consideration. The need for reduced costs and simplified methods for connecting pipelines led to the use of J-tubes. J-tubes are J-shaped tubes attached to a fixed offshore structure, allowing subsea pipelines to be installed inside the tube for connection to surface equipment.

This thesis discusses the J-tube pull-in method for risers and particularly umbilicals. The first part describes the components associated with pull-in through J-tube and gives an introduction to J-tube pull-in analysis. Furthermore, pull-in mechanics and simplified calculation methods for both riser pull-in and umbilical pull-in is described. An introduction to the finite element program Abaqus and how a finite element model can be defined by use of Abaqus keywords is presented.

In the last part of this thesis parametric study of umbilical pull-in is carried out to study the forces that occur during pull-in of an umbilical. Results obtained from simplified calculation and detailed analysis are discussed and compared to each other. It is aimed at identifying the validity range for the simplified calculation method.