An umbilical is an assembly of fluid conduits (thermoplastic hoses and steel tubes), cables (electrical and fibre optic), and power cores, joined together for flexibility and over-sheathed, with or without armouring, for mechanical strength and stability. The emphasis of this paper is on the global configuration design and analysis of offshore umbilicals. The extreme and interference analysis methodologies are presented. One example is given for the application of very small OD electrical umbilical in shallow water in West Africa. The proposed global configurations are presented. Another example is presented for the application of a hydraulic umbilical in deep water in the Gulf of Mexico. The selection of the global umbilical configuration in deep water depends on the host vessel. In other words, the vessel motion characteristics may dominate the umbilical configuration selection for the deep water application. This paper also deals with the influence of the bottom current on the global design of the umbilical in deep water. It can be concluded that an optimized umbilical global configuration, which meets the strength and interference design criteria, can be achieved for the application of a small OD electrical umbilical in shallow water in West Africa as well as for a steel tube designed hydraulic umbilical in deep water in the Gulf of Mexico.

The calculation of fluctuating pressure is necessary during the progress of trip in the managed pressure drilling, because the bottomhole pressure should be constant during the progress of trip. The prediction model of the fluctuating pressure during the progress of trip was established based on the unsteady flowing theory. The actual application state of the prediction model was presented through a computational example. By the comparison between the computational result and the field test result, the computational result matches the field test result very well, which indicates the rationality and the accuracy of the model.