| Offshore oil production activities have expanded tremendously over the last quarter century, and expansion is expected to continue well into the future. As with most natural resources, those which are easily recoverable have been developed, and techniques for the recovery of less accessible deposits are becoming necessary.; Perhaps the simplest method for development of new offshore oil deposits is drilling for oil in deeper water. The limitation in this concept is that as deeper water drilling becomes necessary, conventional fixed platforms become an uneconomic method of recovery. Several different methods, such as the Tension Leg Platform, become more cost effective.; Many designs for Tension Leg Platforms have been proposed, and extensive analyses have been performed for the in service condition under extreme environmental loads. These data can provide significant perspective and hence have been reviewed as a part of this study. However, only one Tension Leg Platform has actually been constructed and installed. Consequently, with this exception, while in service performances for Tension Leg Platforms have been well analyzed, the development and analysis of appropriate installation procedures have been lacking.; The purpose of this study has been the development of an installation sequence for a deep water (365 M) tension leg platform with independent gravity bases. The platform would be floated out to the site with the gravity bases attached, and the bases would be lowered by the tethers.; Tether stresses and base excursions during installation were analyzed for various stages during lowering of the bases, in order to determine the dynamic stresses in the tethers. Stresses during installation turned out to be greater than those during extreme environmental conditions in service. A lowering scheme for the bases was developed which would safely "land" the bases on station while minimizing potential damage to the structure, bases, tethers, and previously installed well protectors.; The finished product of the study consists of two manuals which provide instructions for load out, float out and installation of this specific tension leg platform. |
