Evaluation of concrete buoyancy tank for hybrid riser tower system

This thesis is submitted in partial fulfilment of the requirements for the degree of Master of Science. The thesis sets out the results of a structured programme of research or design, development or management studies demonstrating the candidate's own ability to conduct original investigations, to test ideas (either from the candidate's own or those of others) and to obtain appropriate conclusions from the work. Unlike the situation applicable for theses produced in connection with doctoral degrees, candidates are not required to exercise independent critical judgement in the relevant field of study or to make an original contribution to knowledge. A Master's thesis is not intended to be an absolutely definitive work on the subject to which it relates. Theses encapsulate and present the results of a programme of study and research, undertaken in a defined period of time, and do so in a way that has satisfied the assessment requirements for the degree to which they relate.

In all offshore oil field installations water depth is the economic barrier, onlywhen the demand for crude oil or gas pushes its prices up sufficiently, dooperators take the risk to invest in deeper water and/or new ideas.In the past offshore structures have just been oversized replicas of the alreadyproven design used in shallow waters, such as jacket frameworks and theconcrete gravity base structures. The problem with these structures is that oncethe depth are down to 300 meters and deeper, the structures increase in bothsize and natural frequency. The latter being imposed on by the currents andwaves, hence making them uneconomical. Therefore the need for invigoratedideas become inevitable. This is where the hybrid tower system fits in.In the past few years there has been a lot of effort in optimizing the design andcomponents of the hybrid riser tower system. This thesis facilitates theoptimization process by looking at a different material in which to construct thebuoyancy tank - the material being concrete. A conceptual design is made, andcomparison, where appropriate of the current steel buoyancy tank.