Abstract: A recoverable or permanent rigid subsea form having retaining walls to contain fill material to stabilize, raise and/or provide a level surface above the sea floor. Portions of the retaining walls comprise hollow tanks that are alternately flooded and emptied to control the buoyancy of selected portions of the form. Alternatively, the retaining walls comprise solid plates. Means are provided in the retaining walls for allowing offshore equipment to pass into and out of the form.The form is set in place on or below the sea floor and the fill material is placed in the form. The fill material is leveled by gravity or other means to form a level surface at the desired elevation. Drilling and/or production equipment can then be placed on the level subsea surface.

Abstract: A structure for use in supporting a platform above a body of water is disclosed. The structure includes a leg extending between the bed of the body of water, the seabed, and the platform. The overall cross-sectional area of the leg is greatest near the seabed and decreases moving upwardly away from the seabed.

Abstract: A mobile jack-up drilling rig for offshore use is disclosed using a light, openwork body or superstructure thereby eliminating the requirement that the rig be seaworthy and either partially or totally eliminating the requirement that the rig be buoyant. The jack-up rig requires assistance to be carried to the drill state. The system includes a truss design with little or no hull, using structural shapes for a superstructure whose sizes are dependent on weights and spans. The superstructure is supported by cylindrical, trussed, or other suitably shaped legs. Preload pods, which may be of any shape such as round, may be provided at each of the legs to attach to the superstructure. The preload pods, preferably, support the jacks used to raise and lower the legs.