After the marine disaster of the semisubmersible platform 'Aleksander L. kielland', the Nonvegian Maritime Directorate (NMD) launched a number of research projects on safety of mobile offshore structures One of these was the Mobile Platform Stability project, or the MOPS project. The project was initiated in 1981, and the technical aspects of the project were terminated by the end of 1984. Seven subprojects have been carried out. Icing, Motion Response, Model Tests, Education, Estimation of Damage Conditions, Hydrostatics, and a Project Synthesis. The present chapter describes each technical subproject and the proceedings made during the project synthesis. The main conclusion from the MOPS project is that the present stability regulations of NNID are adequate for the majority of the existing platform types. However, the MOPS project recommends that more rational regulations based on risk analyses, inviting technical flexibility, should be developed in order to increase the overall safety of mobile drilling units in general Projects have been initiated to study this in more detail.


The philosophy of the existing regulations regarding stability of mobile platforms is mainly adopted from the stability rules for ships. The present regulations are primarily based on hydrostatic calculations, and the environmental forces are mainly included as a steady wind heeling moment The dynamic loads are incorporated by a safety factor. One of the main objectives of the MOPS project has been to investigate the technical validity of the present stability regulations, and one important aspect has been to study the dynamics of damaged platforms, both by theoretical means and by use of model test results.

The stability regulations of today have been updated as the rig concepts have changed and as a consequence of increased offshore experience. Another main objective for the MOPS project has therefore been to suggest an outline for possible new stability regulations, allowing for technical flexibility at an early design stage, and also increased safety.

The project has been carried out as a collaboration between several Norwegian research institutions.

The project synthesis has been carried out after the closure of all technical subprojects. In addition to the information from the various subprojects, other projects and institutions have been consulted in order to achieve state-of-the-art. The main objectives of the project synthesis have been as follows.

  • To draw the final conclusions from the technical work carred out in the various subprojects m relation to the stability rules for mobile offshore platforms

  • As far as possible give recommendations on practical use of the results as suggestions for revision of the rules

  • Suggest future research and development projects which can improve the safety level for mobile offshore platforms

The project synthesis has been carried out by establishing a project synthesis group, consisting of all the subproject leaders and personnel from The Norwegan Institute of Technology and the offshore industry.

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