In 1984, the Norwegian oil company Statoil and the Asea Group of Sweden, entered into a general technical cooperation agreement The purpose of this cooperation was to explore the possibilities for advancement within offshore technology by combining the competence and resources of the two companies.

Subsea technology was recognized as a major area of importance as there are plans for more than 100 subsea installations on the Norwegian Continental Shelf alone over the next 10 years On a global basis, this number might exceed 500, of which more than 100 could be installed in water depths of 350–1000 m, thus the potential market and the need for cost-effective solutions was deemed to justify a product development effort Obviously, improved techniques to install and service such subsea installations would in themselves boost the market by reducing costs and simplifying offshore operations Within this context, a joint working group concluded that remotely operated intervention systems offered substantial cost savings and their development would comply with Asea's vast experience in robot technology and design of remotely operated systems With this background, the two companies developed Wellman, a diverless, versatile easy-to-handle and cost effective intervention system The name Wellman (= Wellhead Manipulator) was chosen to indicate the system's flexibility and versatility

The initial development project started in 1985 with conceptual engineering, it proceeded through detailed engineering and manufacturing and was completed following sea tests in Norway during the winter of 1986/87 This paper will highlight the design philosophy, system configuration, tests and further development of Wellman Its cost-effectiveness will also be illustrated

DESIGN PHILOSOPHY

Based on previous studies, the joint development team reached the following conclusions at an early stage

  • The intervention system should be operated from an inexpensive monohull support vessel

  • To replace a subsea installed component a two-trip operation would allow substantial simplification of the intervention system, compared to a one-trip design The additional time required was judged to be marginal, and in many cases the service crew would prefer to inspect the component at the surface before installing a new one

  • The intervention system should be landed and docked on the subsea installation before any subsea operation starts

  • Guidelines and dedicated docking posts were the preferred choice The tool packages should be accurately positioned around the component to be replaced by a three-point docking arrangement Reaction forces should be transferred to the subsea structure

The project team further concluded that

  • Modification of an existing ROV to a common workbase providing power, communication, navigation and handling manipulators, should be the preferred approach

  • Development efforts should concentrate on tools, tool package deployment and system handling

  • The modified ROV with its replaceable tool packages should be easy to handle and operate Fast exchange of tool packages was considered essential

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