Abstract: A semisubmersible mobile offshore drilling unit (MODU) includes a submersible lower hull comprising a ring pontoon having a trapezoidal shape; an upper hull having the trapezoidal shape; three stability columns supporting the upper hull from the lower hull; and a drilling rig. The MODU may be operated in a tender assist mode or an independent drilling mode. The MODU may be equipped to prepare, drill, and complete a subsea wellbore or to workover an existing subsea wellbore.

Abstract: A floating drilling rig configured for performing drilling operations while floating on a body of water is modified to become a converted vessel configured for performing drilling operations while resting on bottom by attaching a support barge component adapted to add rest-on-bottom functionality. The support barge component has a ballast system that alone or by supplementing the ballast system of the floating drilling vessel enables the floating drilling vessel to be ballasted to rest on bottom. The ballast system of the support barge component is adapted to be opened to the water to fill and drain as the water level raises and lowers, and thereby maintain a constant soil pressure. The support barge component may also have a suction breaker system to break suction formed between the support barge and bottom.