Abstract: A method consists in at least partially surrounding a prefabricated structure by means of a floating caisson while leaving a gap of several meters between the caisson and the structure. Then, when the floating assembly constituted by the caisson and the structure is located at the site where the structure is to be grounded, the assembly is positioned and oriented approximately and the caisson is grounded on the sea bed or on a river bed by ballasting. Thereafter, the structure is grounded on the bed accurately in position and in orientation by ballasting the structure while using the grounded caisson as a fixed point for positioning and orienting the structure. This method may be used for accurately grounding a foundation for a bridge pier, and it also makes it possible to prefabricate and assemble a bridge superstructure (pier, pylon, deck, shrouds) on land or in a harbor, with the superstructure being temporarily supported on the caisson.

Abstract: A marine operations structure for use in arctic seas having steel/concrete composite ice walls positioned to permit multi-year ice ridges to be broken up with lower vertical forces imposed on the structure than heretofore possible. The structure provides for simultaneous contacting and fracturing of both surface ice floe and multi-year ice ridges by proportioning of the ratio of the annular dimension of a first sloped surface to the radius of the structure within the range of about from 0.15 to 0.30. The structure is fabricated by modular construction techniques which lowers total construction costs. The structure is in the form of a sixteen-sided polygonal sloped walled marine structure with internal ballast tanks for providing gravity founding of the structure on the sea floor. Modular drilling equipment is provided for and supported by the structure for use through two rectangular shaped moon pools extending vertical throughout the central core of the 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.

Abstract: A platform for use as an artifical island wherein the platform comprises an immersed base of floats, vertical pillars and an emerged structure supported by said pillars. The floating base is formed by a disk of caissons. The vertical pillars are imbedded in the caissons and form the generating lines of a cylinder of substantially circular base. The emerged structure comprises a lower disk-shaped part traversed by the pillars, and an upper part comprised of modules which are joinable together to form a cylindrical assembly resting on the pillars. The floating disk may be dimensioned in relation to the platform and to the marine characteristics so as to offer low draft and high stability. Such dimensioning enables the platform to be entirely constructed in a shipyard and subsequently towed to the installation site.

Abstract: An offshore bulk liquid discharge system and method for its deployment are disclosed. The system is adapted for rapid deployment and facilitates rapid unloading of liquids from an ocean tanker to a shore location. The system includes a base, a mooring buoy tethered to the base and floodable buoyancy tanks which may be flooded causing the base to land on the sea floor. A product swivel mounted on the base provides fluid communication between a tanker hose and a flexible pipeline.

Abstract: A hybrid offshore structure for conducting petroleum drilling and producing operations in very deep waters is disclosed. The structure consists primarily of a substantially rigid lower section extending upwardly from the bottom of the body of water to a pivot point located intermediate the bottom and the surface of the body of water, a compliant upper section extending upwardly from the pivot point to a deck located above the water surface, pivot means located proximate the pivot point and adapted to permit the compliant upper section to pivot laterally in response to environmental loads, and torsion means adapted to transmit torsional loads from the compliant upper section to the substantially rigid lower section. The lower section may comprise either a conventional trussed steel frame fixed to the bottom of the body of water by a plurality of piles or a concrete or steel gravity base. The compliant upper section may optionally be either a guyed tower or a buoyant tower.

Abstract: At least two generally parallel compression rims are joined by tension element spokes, such as cables. A rim separating means, such as columns, holds the rims apart thus maintaining spoke tension. The resulting structural element, comprising rims, tension elements and separating means, becomes an efficient means of transferring external forces from one rim to the other.

Abstract: An improved offshore platform base (12) is disclosed having three sets of substantially parallel bulkheads (24, 26, 28) which intersect one another at about 120.degree. forming a repeatable array of contiguous triangular (30) and hexagonal-shaped (34) chambers.

Abstract: A monolithic structure for off-shore mooring composed of a broadened foundation (2) and an emerging vertical structure (1) having a very slender character and a flexural resistance modulus decreasing from the bottom towards the surface. This structure has a buoyancy chamber (15) placed in a submerged position and close to the top end.

Abstract: An offshore structure and method of constructing same are disclosed. The offshore structure comprises a jacket assembly, a bottom tank secured to the bottom of said jacket assembly and a movable tank which is vertically slidable along said jacket assembly and which can be positioned on said bottom tank as a ballasting and storage tank. The offshore structure further includes a guide mechanism between said jacket assembly and movable tank to guide the vertical sliding of said movable tank, a frictional plate disposed on the contact surface between said bottom tank and movable tank so as to permit the two tanks to slide relative to each other in a given horizontal movement, and a buffer disposed between said jacket assembly and movable tank.

Abstract: A bottom-seated portable cofferdam is disclosed along with a method of using the cofferdam for providing working access to underwater surfaces which are generally horizontal. The cofferdam includes a housing having a bottom opening with a skirt extending about its periphery, first and second seal means being secured to the skirt in spaced-apart relation to form a differential pressure chamber open along its bottom. In use, the cofferdam is first positioned adjacent the underwater surfaces, water then being evacuated from the chamber in order to develop a differential pressure therein for urging the cofferdam into engagement with the underwater surfaces.

Abstract: A semi-submersible offshore platform comprises an operating deck carried by four cylindrical columns supported by a pontoon structure comprising four-sided boxes formed into a square ring. Each pontoon box is subdivided into two compartments by a longitudinal centerline bulkhead, the compartments being further subdivided into tanks by transverse bulkheads. Tanks outside the centerline bulkheads are used for ballast water, and tanks inside the centerline bulkheads are used to store the oil produced.

Abstract: An offshore platform structure of the gravity type intended to be installed on a sea bed in artic or corresponding waters. The platform structure comprises a substructure intended to be completely submerged and supported by the sea bed when in installed position, a superstructure extending up from the substructure and up above the sea bed and a deck superstructure supported by the superstructure above the sea level. A fender is provided intended to protect the superstructure against drifting ice and icebergs, the substructure being provided with a preferably horizontal top support slab supporting the fender, the fender being movably arranged on said support slab and comprising a preferably compartmented cylindrical ring-shaped body with a large weight resting preferably freely on the substructure, intended to be arranged apart from the superstructure when in normal position.

Abstract: The invention relates to a method for pre-loading the legs (2,3,4) of an artificial island (1) to increase the stability of the island preloading is performed by ballast (7-17) placed in or on the legs, this ballast being preferably located within flexible bags (17,18,19,22,23,24,25,26,27,33,34,48,49,50,51) placed upon the trussed members (11,12,13,14,15,16) of the legs or upon a plateau (46) supported by beams (45). Instead of bags a rigid receptacle formed by plates (37-40) can be used for receiving ballast. Furthermore, the hollow tubular members (52,53,54,55) can be used for receiving liquid ballast.

Abstract: The structure is made in several "storeys" (D1, D2, D3). These are floated away from their construction site in conventional manner. Once in sufficiently deep water, the storeys are tilted over so that they float on their side, and they are then joined together end-to-end. With tilting and rotating operations performed by suitable ballasting and unballasting of compartments in the storeys, the joining operations can all be performed on members at or near (just above or just below) the surface of the water. Once the storeys are assembled together, the entire structure may be towed on its side to a point of use, and then immersed so that it stands vertically on the sea bed.

Abstract: A lightweight drilling structure for use in offshore arctic waters comprising a lower frustoconical section and upper section wherein the lower section is towed to location, ballasted to sink in place on the sea floor and anchored in position by flooding the stability compartments. The upper section containing the drilling rig and equipment is then floated into place over the lower section, ballasted to rest on the lower section and the two sections sealed and fastened together. The assembled structure is firmly anchored in place by dewatering chambers located in the bottom of the lower section to create a suction between the bottom of the lower section and the ocean floor.

Abstract: A concrete offshore structure located in a body of water of selected depth and extending from a bed defining the bottom of the water body to above the water surface comprises at least two similar prefabricated concrete modular subassemblies interconnected in a vertical arrangement in such manner to define a horizontal interface between each such pair of subassemblies. vertically disposed shear resistant pin means between the subassemblies and cement at the interface secure them together.A method for deploying such a structure includes towing the subassemblies offshore, mating them, and towing the assembled structure to the selected offshore installation site.

Abstract: The specification discloses a single point mooring for vessels comprising a base member adapted to rest on the ocean bottom, a cross member joined to the base member at one end thereof and a mooring post member joined to the base member at the opposite end and perpendicular to a plane intersecting the base member and cross member. Placing the single point mooring by floating, towing and sequential flooding is also disclosed.

Abstract: The invention relates to a method for the building and putting in place of a sea platform in using buoyancy chambers. The buoyancy chambers are temporarily attached to the raft and capable of being ballasted for allowing the control of their buoyancy during the building of the structure and their recovery. Simultaneously with the building of the tower and walls, the chambers are progressively built by assembling of portions of bodies mounted on a bottom element resting on a chamber receptacle.

Abstract: A marine fluid transfer buoy is anchored to the sea bed employing two vertically displaced cardan joints. Connection between an undersea pipe and the fluid transfer buoy is made coaxial with the lower cardan joint and connection to a riser pipe to the surface is made coaxial to the upper cardan joint. All twist in the conduit at the connections is accommodated within a pressure container intersected by the two cardan axes which provides a protected dry environment for the conduit within.

Abstract: A marine structure includes a base which is to be founded upon the sea bed. An elastic pre-stressed column is rigidly fixed to and extends upwardly from the base. A buoyant, rigid structure is fixed to the upper end of the upstanding elastic column. The buoyant, rigid structure includes a submerged part and a part projecting up above the sea level to support a deck superstructure. The pre-stressed elastic column is designed to deflect in a curved manner when the buoyant, rigid structure is subjected to environmental forces. In particular, the first nautral period of the installed structure is longer than the significant exciting wave periods. Accordingly, the main structure will oscillate about its vertical equilibrium when subjected to waves and wind thereby behaving as an articulated column.

Abstract: An offshore structure is provided for handling cryogenic fluids such as liquefied natural gas. The structure comprises a lower section of concrete and an upper section which projects up from the lower section above the sea level to support a deck superstructure. The lower section is formed of a plurality of cells and at least one of the cells houses an insulated tank for the storage of low temperature fluids. The tank or tanks are completely submerged when in operation and are rigidly supported by the associated cell. Each tank comprises a primary and secondary barrier with insulation associated therewith and the tank(s) communicates with the deck superstructure through an access tunnel system.

Abstract: Oil and gas extraction from deep water sites. Various structures and equipment are described, including vessels for oil/gas storage beneath the surface and/or conduction to the surface, concrete being extensively used in the construction of the structures. A joint is described that articulately connects a structure to the sea bed or to another structure.

Abstract: A folding sea-floor compactable template for proper positioning and spacing of subsea piles and wells in the sea floor. Anchor pile templates or well templates are provided at the end of long hinged arms which extend radially out from a central section (which may also be used as a well template). The arms are folded back over the central section for transportation. Flotation can be in the main central section. With additional flotation at the outer ends of the arms, installation can be carried out by controlled submergence in stages from a single barge.

Abstract: Apparatus for constructing an island in a body of water including a plurality of caissons and means for connecting the caissons in an end-to-end configuration to form a ring. Once the caissons have been connected together to form a ring and ballasted to set the caissons upon the bottom of the body of water, sufficient fill material is placed inside the ring of caissons to construct an island in the body of water.

Abstract: An off-shore gravity type platform for supporting a processing installation above the surface of a body of water and for housing processing components, comprising a pressure-resisting watertight central shaft extending from top to bottom of the platform structure, the lower end of the shaft being surrounded by a coffered base structure with a protective wall surmounted by pillars co-operating with the shaft for supporting a bridge, the shaft being so sized that the platform has a positive buoyancy, the top of the protecting wall being located below the level of the body of water, and the pillars being hollow and being filled with concrete after the platform is in place.

Abstract: The method uses a construction and launch barge having a shallow draft hull with a construction deck supporting at its center a floatable offshore structure both during construction thereof and during the towing of the barge to the site where the offshore structure is to be installed. In order to maintain stability, a plurality of hollow column stabilizers are provided on the barge; these may be, e.g., four, one adjacent to each corner of the barge and extending up high thereabove. Large offshore structures of concrete are constructed on the barge in relatively shallow water and then towed across relatively shallow water to a desired location and then the barge is separated from the offshore structure by sinking the barge to a sufficient depth, releasing the then-floatable offshore structure from the barge, and then displacing the barge away from the offshore structure. Then the barge is raised again and returned to shore. The offshore structure may then be lowered into its operating location.