Design of bore selector for tordis vigdis workover system

Abstract

The cost of the workover system and the time required to run the workover equipment constitute a significant component in the subsea workover/intervention cost. But, the cost can be minimized by modifying traditional equipment configuration and design. Bore selector is one such concept, which helps to reduce the cost of the subsea workover system. The concept of the bore selector is designed for shallow water depth and reservoir conditions of the Tordis Vigdis field. Currently the Tordis Vigdis workover system does not have a bore selector and both the production and annulus lines are accessed separately using dual bore workover riser. The novel steps in the development of a bore selector for this workover system are discussed in the thesis. During the design process, the study for the best location of bore selector in the workover system is investigated and found out. Subsequently, different concept has been developed, and the best one is selected for design based on evaluation criteria. 3D model of the selected bore selector is built with the help of the drawing tool ‘Creo Element/Pro’. The wall thickness of the selected model has been verified against API and ISO standards with the chosen yield and tensile strength values to with stand the internal and external pressure. Pressure design calculation is done for different operating conditions viz. normal, extreme and accidental with corresponding design factors to ensure that the design is within acceptable limits. The thesis, thus explains the preliminary design work for a bore selector in Tordis Vigdis workover system.