Abstract

A drilling contractor has collaborated and consulted with several major operators, engineering firms, a classification society, and a shipyard to develop the design and specifications for a mobile offshore drilling unit capable of working in both Arctic and tropical environments. Significant design challenges in the area of heating and ventilation were identified and existing known solutions for exclusively Arctic based vessels were found to be inadequate for a drillshipoperating over this range of conditions. This paper will explain how a suitable design approach was developed that satisfies the range of temperatures and other ancillary ambient environmental and HSE issues associated with such a wide range of operational requirements.

Background

Arctic operations will subject the hull and industrial systems to icy and ice covered waters with design air temperatures as low as −40°C, while off season operations outside of the Arctic regions require accommodation of warm waters and an ambient air temperature of as high as +38°C.

For the ship's crew to be able to operate effectively and safely in the winter extreme cold temperature, the design team determined that normally manned areas must be enclosed and heated to a minimum of at least +5°C.

Enclosing most areas does not create significant design problems; however, this paper will cover environmental challenges discovered for storm conditions and in enclosed areas on the rig subjected to cyclic changes in air pressure and temperature and how these issues were resolved.

Results, Observations, and Conclusions

Given the two extremes of severe winter and tropical conditions, the severe winter case was found to be the driving factor in developing a workable design, with limited heating capacity and while also meeting the Class required air exchange rates. These sometimes conflicting objectives have been addressed and resolved successfully after consideration and development of the methods described herein.

Significance of Subject Matter

D ue to seasonal limitations for drilling operations in Arctic offshore waters, the economics of the current offshore market require a vessel that is also capable of working in mild to tropical conditions in annual off-season periods. High standards for crew habitability, ergonomics, and HSE have been applied to meet modern expectations.

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