Abstract

This paper is the first phase report in the investigation of Tension Leg Platform in CSSRC. A series of tests and computational work have been Platform in CSSRC. A series of tests and computational work have been performed for a four column TLP in 256m water depth under the influence of performed for a four column TLP in 256m water depth under the influence of waves.

Attention was paid to investigate the effect of variation of pretension of tether load and pontoon configuration on the behaviour of TLP in waves. Survival condition for the TLP was also investigated, including a case study of leg failure in storm waves.

Results of computations based on 3D potential theory by CR-WAVE safe compared with results of model tests. The applicability of the method is confirmed.

Introduction

With exploration of oil into deeper seas, TLP is a promising system which has been widely investigated by the Western World. It is thought that such system would find great usage in the South East Asia Seas as well. Therefore a long-term project was undertaken by CSRC since 1982 under the auspices of the China National Economic Committee to meet the demand. Examples of the Research and Development in the world are: the Conoco TLP scheduled to operate at the North Sea Hutton Field, the design of Tecnomore (1) for a water depth of 600-1000m. In addition, much research work is being carried out in the Netherlands (2), (3), Japan (4), (5) and Norway etc. A review of the state-of-art may also be found in (6).

In design a tension leg platform a good knowledge of the motion behaviour and tether load is important, whereas its pitch, roll and heave responses are quite small relative to sway, surge and yaw responses. Emphasis was, therefore, paid on the horizontal modes of motions in our investigation. It was also noted that the survival conditions are critical to the safety of platform in heavy storm, different situations were assumed as the test platform in heavy storm, different situations were assumed as the test conditions, including storm wave tests at the highest waves in 100 year return period in South China Seas and tests in the failure case of one leg in the storm condition. The behaviour of the TLP after one leg failure was also studied.

In view of lack of information in regard to the influence of the variation of pretension sand pontoon configuration on the behaviour of TLP in waves, this paper deals also with these problems on the basis of the experimentation and some comments are made in this respect.

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