ABSTRACT
Most offshore drilling in shallow to moderate water depths is performed from self-elevating mobile jack-up units. They are also used for fixed platform work-overs and increasingly for production support. Jack-ups are towed to site floating on the hull with the legs elevated out of the water. On location, the legs are lowered to the seabed, where they continue to be jacked until adequate bearing capacity exists for the hull to be lifted clear of the water. With jack-up and spudcan sizes fixed, the pre-loading level reached is critical to any site-specific assessment of the jack-up capacity to withstand a design storm. Before a jack-up can operate at a given location, a site-specific assessment of its operation must be performed. This continual assessment is what differentiates jack-up analysis from that of conventional fixed platforms and most onshore operations.
