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Figure 1.2 - Jack-up platform “Blake Rig 303” with tubular legs

A Jack Up is an offshore structure composed of a hull, legs
and a lifting system that allows it to be towed to a site, lower its
legs into the seabed and elevate its hull to provide a stable work
deck capable of withstanding the environmental loads. A typical
modern drilling Jack Up is capable of working in harsh
environments (Wave Heights up to 80 ft, Wind Speeds in excess of
100 knots) in water depths up to 500 feet. Because Jack Ups are
supported by the seabed, they are preloaded when they first arrive
at a site to simulate the maximum expected leg loads and ensure
that, after they are Jacked to full air gap and experience operating
and environmental loads, the supporting soil will provide a reliable
foundation. Jack Up Units have been a part of the Offshore Oil
Industry exploration fleet since the 1950’s. They have been used
for exploration drilling, tender assisted drilling, production,
accommodation, and work/maintenance platforms. As with every
innovative technology, Jack Up Units have been used to their
operational and design limitations. These limitations include deck
load carrying limits when afloat, load carrying capabilities when
elevated, environmental limits, drilling limits, and soil
(foundation) limits.
The reasons for pushing these limits include the desire to
explore deeper waters, deeper reservoirs in harsher environments,
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