Abstract: A method and apparatus for installation of heavy, ballastable, gravity fundament structures on the sea bottom at large depths. In accordance with the invention, there is utilized air, water, and a liquid lighter than water in various proportions and combinations to provide the structure with the required buoyancy and submerged weight during the sequential phases of the transport and descent operations in order to finally position the structure in a selected location on the sea bottom. Various modes can be used to accomplish the descent and the structure may in a final stage be penetrated down into the sea bottom to a sufficient degree.

Abstract: A method for fabricating and installation of a floating bridge or the like provides that a bridge superstructure is supported by a number of pontoons and has opposite ends anchored to shore fundaments. Prefabricated pontoons are positioned successively at mutually spaced locations on the water surface along a center line of a part of the bridge superstructure being formed. Such pontoons are suitably ballasted. Further bridge superstructure is fabricated successively in sections in a production unit positioned on a barge or on a platform stationarily positioned by the shore. Such sections are being pushed outwardly of the production unit one after the other, with a new section being made as a continuation of a preceding section. The fabricated part of the bridge superstructure, formed of several interconnected sections which gradually are protruded from the barge or platform, is slid or pushed out onto the pontoons that are positioned one after the other, and are mounted thereon.

Abstract: The immersion and positioning of a sink element on the sea bottom is controlled by providing a weight system suspended from the sink element. An auxiliary surface vessel has a control cable directly connecting the vessel with the weights system suspended from the sink element. The sink element is immersed with the weight system suspended therefrom and therebelow until the weight system contacts the sea bottom and the sink element reaches a preselected stabilized equilibrium elevational position above the sea bottom. Then the sink element can be laterally displaced while substantially maintaining the height of the sink element above the sea bottom by having the auxiliary surface vessel pull on the control cable connected to the weight system in a direction of movement towards the final location site. The weight system contacts the sea bottom during this movement to help control the movement of the sink element and minimize the influence of outside forces.

Abstract: A large, curved or spherical shell of reinforced concrete is cast without utilization of supporting framework. A casting formwork is in the form of a thin, suspended membrane that is reinforced with a collar. During construction and transport, the membrane is preliminarily equipped with a reinforcing compression ring.

Abstract: An oil storage system for an offshore platform having at least one submerged storage cell in which oil is stored on top of a water volume. In fluid communication with the submerged storage cell is another submerge cell containing water, the water storage cell is in fluid communication with ambient water outside the system.

Abstract: A tension leg platform for drilling and/or production, processing and transporting hydrycarbons from sub sea wells or installations, and methods for installation of such platform. The platform comprises in operational position the following: a working platform which has position above the sea level, a buoyant body (1) which is connected with the underside of the platform and has substantially position below the surface, and a number of tension legs (13) which connect the buoyant body (1) with a fundament anchored to the sea bed. The invention is characterized in that the lower parts of the tension legs (13) in per se known fashion are anchored to the fundament (14) and at their upper ends are controlled in guides (20, 21) on the outside of the buoyant body and are attached to the buoyant body (1) above or just below the water line.

Abstract: A method of installing a floatable or buoyant body on the sea floor includes towing the body to an installation site at the sea surface and subsequently submerging the body towards the sea floor by supplying ballast to the buoyant body. The supply of ballast is discontinued when the buoyant body reaches a preselected sinking velocity and the vertical movement of the buoyant body is discontinued at a predetermined level above the sea floor by a floating vessel or the like which is floating at the sea surface. One end of the vessel is connected to the buoyant body by a connector system, the length of which is smaller than the sea depth at the installation site. The buoyant body is displaced laterally to a preselected final location, whereafter the buoyant body is further submerged towards the sea floor until the same is positioned on the sea floor at a preselected installation site.

Abstract: An offshore platform structure of reinforced concrete for standing on the bottom of a sea as a consequence of its own weight. The structure includes a base supporting a tower for a platform deck. The lower part of the tower includes a cylindrical portion extending downwardly towards and through the base and providing a skirt. A frusto-conical annular wall extends coaxially with the tower between the tower and the top of the base to provide an annular chamber with a triangular cross section. Also a method of building a platform structure includes building the lower portion of the structure in a dry dock and floating the lower portion out into deeper water for continuing a casting operation for the remainder of the platform structure.

Abstract: Method for founding and stabilizing an off-shore platform which at its lower end is provided with skirts. The skirt or skirts are forced so deep down in the ground that a significant portion of the foundation area is transferred down to a depth where the load carrying strength of the ground is sufficient in regards to geotechnical stability and that it prevents an acceptable settlement.The platform (1) which is intended to be installed at very great depths, includes a foundation structure to be forced down in the sea bed, a cell portion that in its operational position is completely submerged, and an upper portion extending from the cell portion and up above the sea surface, where the submerged cell portion includes a centrally located cell surrounded by at least one cell portion.