Method and apparatus for removal of submerged offshore objects

Abstract

A method for removal of large metal objects such as offshore platforms that may be embedded in or substantially immobile and lying on the seabed. The environment should be dislodged from at least a portion of the supporting pile embedded below the mud line. A liquified gas is injected into the environment in contact with the pile to embrittle the pile. Upon embrittlement, the pile is fragmented. Thereafter, the pile may be removed from the seabed. A cannister for use in the above method has a body shaped to conform to the pile or object to be fragmented and contains liquified gas to be sprayed from nozzles by a pressurized gas to chill the object to be fragmented upon embrittlement. A support is positioned on the body for raising and lowering the cannister within the pile. A fragmentation tool for insertion into the pile or other object to be removed from embedment in the sea and having a plurality of anvils housed in open ended elongated tubes, a propulsion means generating gas pressure, a frangible connection that ruptures when sufficient pressure is generated to propel the anvils to strike the embrittled area and cause fragmentation. An apparatus for applying tension to the pile before fragmentation consists of one or more hydraulic rams connected between the pile and the concentric jacket.