Jack-up rig for marine drilling

Claim 1

A mobile jack-up rig, for marine drilling, of the self-elevating type having a floatable hull, legs which can be propelled from transport positions projecting above the hull downwardly to engage the bottom of the sea to serve as bases for use in jacking-up the hull to a stable drilling position substantially above the water surface, said rig being fitted with conventional devices and equipment for marine drilling of oil wells characterized by comprising a special system which allows the conversion of a drilling derrick into a high capacity crane and vice-versa, said special system comprising the following members: (a) a drilling derrick attached to a movable structure on a drilling deck by means of pivots which permit it to be tilted in order to be changed into a crane boom; (b) a drilling winch provided with two drums which act separately including a main drum which actuates the wire lines that move the travelling block and a secondary drum which actuates the wire lines that move the parts which perform swabbing operations, directional logging, movement of parts along the well, etc.; (c) a drilling deck mounted on a swivelling base capable of rotating 360° in any direction, said swivelling base also forming the rotating crane table when the assembly formed by the drilling derrick and the drilling deck is acting as a crane; and (d) a movable substructure over which said swivelling base rests, said movable substructure being provided with a motor which transmits rotating motion to the swivelling base, this motor also being designed to drive the substructure on rails along the deck whenever it is necessary for the operation of the rig in the crane mode.