X-Y Skidding System

The idea behind the X-Y cantilever is simple: it can move in two directions instead of one. It is not only possible to extend the cantilever with the derrick in a longitudinal direction (the X-direction), it can also move in a transverse direction over the width of the deck (the Y-direction). The effect is huge. The X-Y cantilever has approximately twice the drilling envelope than a conventional cantilever. The jack-up, therefore, needs to be moved less frequently.

The additional advantage is that the derrick is always located near the centerline of the cantilever, thus the weight and loads are always evenly distributed. As a result, the cantilever steel weight is lower, the combined load is constant over the transverse reach and the longitudinal reach is greater. The capacity of the X-Y cantilever is approximately 1.5 times higher than a comparable conventional cantilever.

The position of the X-Y cantilever above the main deck is higher than a typical cantilever. This, together with the reduced width of the cantilever, minimizes deck obstruction. The required air gap of the hull is also minimized for work over an existing jacket. This reduces the length of leg below the hull and therefore also the overall loading on the jack-up.