This paper describes the development of a jack-up design philosophy. An overview of design aspects in the various modes of operations is given.
As example the development of two series of jack-up designs for hostile waters is discussed.
The jack-up is (one of) the oldest mobile offshore platforms (ref.1). Since the first unit in 1955 the number of units active in exploration and production drilling has grown to 460 in 1983 (ref.2). production drilling has grown to 460 in 1983 (ref.2). As compared to other mobile offshore platforms the jack-up can be characterised as a highly mobile self-installing and, most of all, a steady and stable platform for offshore operations.
In the years from 1955 to 1983, the jack-up has developed from a platform for 30m waterdepth moderate environment to a platform for 100m waterdepth harsh environment, as found in the northern North Sea or offshore Canada.
At first sight, present designs do not differ too much from the very first. The essential elements still have the some appearance:
the buoyant hull accommodating derrick, drilling equipment, power plant and accommodation
three or more legs of an open truss type structure.
In reality, however, in the struggle to reach deeper and harsher waters at an economically acceptable level, the evolution in:
elevating systems and
has been tremendous.
The essentials of all present capabilities of the industry are combined into a lack-up design, in the conceptual design per se. This paper describes the design philosophy as used by MSC in the development of their jack-up designs. As examples two design series are discussed in more detail. To set the scene, this paper starts with an inventory of design aspects of the various operational modes of a jack-up.
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