Abstract: A drilling vessel is provided for selectively drilling two or more wells from a single location of the vessel, comprising a buoyant hull having a deck, including ballasting devices in the hull for allowing the vessel to be stabilized on the bottom surface of a body of water; a movable substructure in contact with the deck, wherein the movable substructure includes a drilling platform having a plurality of downwardly extending support legs attached thereto, wherein the height of the drilling platform from the deck is sufficient to allow simultaneous drilling and production activities to occur; and a repositioning system, operatively connected between the support members and the deck, for moving the drilling platform in a predetermined direction relative to the deck. In a preferred embodiment, a plurality of lift and roll jacks are employed beneath each level of a two-tiered repositioning system such that the substructure may be moved in both a transverse and a longitudinal direction.