Abstract: An off-shore ice island structure for location over a submerged drill site in waters which normally freeze in winter. The structure includes a buoyant protective caisson which freezes in position over the drill site upon onset of winter. A barge floats on water kept unfrozen within the caisson, and is connected to the caisson so it can be swivelled generally about a vertical axis to adjust the circumferential location of the drilling axis of drilling apparatus carried on the barge. The drilling apparatus is movable relative to the barge to enable further adjustment of the drilling axis location. The arrangement enables the drilling axis to be maintained in substantial vertical alignment with the drill site despite movement of the caisson caused by the surrounding shelf ice. The caisson is part of an ice island structure whose mass is built up by successive flooding and freezing steps to ground it on the sea bed.

Abstract: A method and apparatus for forming an off-shore ice island structure in waters which normally freeze in the winter. The ice island is useful as a base for oil field operations, for oil and gas storage, for docking ships during thaw periods, and the like. The structure comprises a plurality of elongated hollow wall elements adapted to be vertically oriented and assembled in open water to form a bounded area. The elements become frozen in place during the winter and the bounded area is intermittently flooded at intervals to permit accumulation of ice sufficient to sink the ice island to the marine bottom. Additional wall elements are added to the first wall elements to form upward continuations to contain the flooding water and accumulated ice. Pumps are provided to convey water to the upper surface of the island for freezing, and to carry off brine during the freezing process. Refrigeration equipment can be utilized to keep the ice island in a frozen condition during seasonal thaws.