Abstract: A mobile, self-elevating, offshore production platform, for exploitation of smaller reservoirs, is provided with a liquid tight hull having a deck; a plurality of support legs, each having a gear rack and bottom footpads, which are slidably extendable through the hull; a removable jacking tower for each support leg, and, a locking means for each support leg which is engageable to the leg gear rack at any vertical position of the leg. Mineral processing equipment is pre-installed on the deck at a suitable shoreside facility. Then the platform, with legs elevated, is towed to the offshore location where minerals are to be produced. On location the legs are lowered, grounded, and then pre-loaded to desired criteria by introducing ballast water into the hull. After pre-loading the platform is deballasted and elevated to establish a desired air gap.

Abstract: A Heave-Restrained Platform and Drilling System (HRP/DS) comprises a floating structure having a central buoyancy means, at least three out-rigger columns, and a hybrid mooring system in which a spread (lateral) mooring system functions with an array of tensioned production risers (serving as a vertical tension leg) to keep the structure generally over a specified seabed location. The HRP/DS provides a means for drilling and producing through oil wells in deep water such that critical pressure containment means are achieved with safe, redundant barriers and systems similar to those employed on shallow water fixed platforms.

Abstract: A submersible production storage barge and method for transporting and installing a jack-up rig in a body of water has the submersible production storage barge releasably secured to a jack-up rig while the jack-up rig and submersible production storage barge are towed as a unit to the desired offshore location.

Abstract: A modular near-surface completion system that positions the production wellheads in a quiescent zone beneath significant wave activity yet within reach of divers for maintenance and inspection. Each subsea well is provided with (a) its own riser, (b) a riser tensioning buoy and (c) a production well tree mounted atop the riser buoy. Produced fluids are transmitted from the well tree to the floating production platform by means of flexible risers suspended in a catenary loop of sufficient length to permit the platform to be maneuvered to position it for drilling or workover of any of the plurality of templates it services.

Abstract: A method and apparatus is set forth in the present invention for supporting the weight of a marine riser by use of a passive tensioning system which utilizes a buoyant member located upon the upper end of the riser. The member has a vertical slot defined through its side such that the riser may access the member from a lateral direction. Such lateral access of the riser to the member allows these buoyant members to be changed from beneath the riser when maintenance and/or inspection is required on a particular member.Since the riser need only to move laterally to access any member, and the riser may be temporarily supported at the surface by other means, the lower end of the riser does not need to be disconnected from subsea equipment when maintenance and/or inspection operations are required on a buoyant member. Well operations do not need to be interrupted, therefore, during buoyant member maintenance operations.

Abstract: A floating platform structure mounted on ballast tanks disposed in a tank having the liquid to be mixed and/or aerated by an impeller carried by the platform. Guide members on the structure have longitudinally spaced sets of rollers slidably engaging upstanding posts in the tank and restrain the platform against rocking or horizontal movement due to wind or wave action, while allowing the platform to rise and fall with changes in the level of liquid in the tank.

Abstract: A tension-leg offshore platform comprises a positively buoyant, floating upper unit in which an operations platform is supported above an ocean surface by a plurality of spaced vertical columns defining buoyancy chambers. The lower ends of the columns are connected to the ocean floor by a corresponding plurality of tension-leg assemblies. Each tension-leg assembly is comprised of a plurality of positively buoyant tubular members having their lower ends connected securely against upward movement to the ocean floor. The tubular members are of substantially equal length less than the pertinent water depth by an amount adequate to cause their upper ends to be located below the area of significant surface wave action yet substantially above the ocean floor. A separate flexible tension member for each tubular member connects the lower ends of the columns to the upper ends of the corresponding tubular members.

Abstract: A method and apparatus for the mounting of lift cranes on jackup rigs, offshore platforms, and like offshore structures provides a first static bearing race portion which is mounted upon the jacking structure, for example, of a jackup rig surrounding the telescoping leg associated therewith. On offshore platforms, a vertical leg portion of the jacket can be extended vertically with the static bearing race portion being affixed to the extended vertical jacket leg. A second movable bearing race portion is attached to the static race portion with a plurality of bearings therebetween allowing the first and second bearing race portions to rotate with respect to one another. The crane is then supported on the upper bearing race portion with the telescoping leg of the jackup rig or offshore jacket structure passing through both bearing race portions, the crane structure unencumbering vertical movement of the leg in the case of a jackup rig.

Abstract: Improvements in an offshore platform and submarine storage facility for highly chilled liquified gas, such as liquified natural gas, are disclosed. The improved facility includes an elongated, vertically oriented submerged anchoring frame to which one or more insulated storage tanks are moveably mounted so they can be positioned at a selected depth in the water. The double piston tank is constructed with improved seals to transfer ambient water pressure of the selected depth to the cryogenic liquified gas without intermixture. This transferred pressure at the depth selected aids in maintaining the liquified state of the stored liquified gas. Structural improvements to the tank facilitating ballasting, locking the double piston cylinders together and further facilitating surface access to the tank for inspection, repairs and removal, and structural improvements to the platform are disclosed.

Abstract: An offshore submarine storage facility for highly chilled liquified gas, such as liquified natural gas, is disclosed. The facility includes an elongated, vertically oriented submerged frame. An insulated storage tank is movably mounted to the frame so as to be positionable at various depths in the water. The tank is constructed to transfer external ambient water pressure to the liquified gas without intermixture. This transferred pressure aids in maintaining the liquified state of the stored liquified gas.

Abstract: Control forces for stabilizing semi-submersible platforms are provided outboard the platform columns, at a point approximately where the free surface of the water intersects the columns, without altering the internal arrangements or structure of the platform and employing equipment which develops pressures needed to impose control forces only. In a similar manner, control forces for stabilizing pitch and roll motions in ships and to effectively damp the oscillatory motion of the water level in a "moon pool" are provided.

Abstract: A platform comprises a base structure designed to rest on the bottom of the sea for supporting an industrial or scientific installation above the surface of the water. The base structure comprises a floatable device capable of keeping afloat and means for ballasting the base structure to install the structure on the bottom of the sea. The base structure also includes a shaft in which a hollow element with a water-tight peripheral wall and a water-tight lower end wall, can slide vertically. The element can be temporarily fixed to the shaft. The element forms a float capable of supporting a deck which carries the installations, but is capable of being immersed over at least the greater part of its height. The deck is capable of floating until it is over the top of the element when the element is immersed and has means for fixing it to the top of the element.

Abstract: A gravity platform for supporting installations above a body of water, comprising a base for resting on the bed of the body of water, a structure secured to the base and rising vertically therefrom, a bridge provided with float means, and means enabling the bridge to be displaced along the structure, the base consisting essentially of a slab provided with stiffeners, such as a circular wall and diaphragms, essential for its mechanical strength, the structure forming a hollow column, impervious or not, rising from the middle of the platform, and the float means consisting of an impervious shell formed around the hollow column at the lower part at least of the bridge and forming, possibly with said hollow column, if it is impervious, a float the buoyancy of which is sufficient to support the assembly of the platform and its installations.

Abstract: A method and apparatus for fabricating an offshore structure intended to be installed at sea comprising a support structure and a platform mounted on the structure. The platform is made up of one or more pieces that are floatable in water. The support structure is immersed to a depth sufficient for the portion thereof intended for the reception of the platform to be situated near the level of the latter. The platform is then fixed to the support structure which is then made lighter and brought to the place where it has to be installed.

Abstract: A buoyancy system is disclosed for use in controlling the descent and ascent of an object, such as a pipe line being laid offshore. The system includes a plurality of inflatable, collapsible, submersible buoys which may be remotely controlled by air or other inflating mediums. As each of the buoys, and thus the load connected thereto, is lowered or raised in a body of water the pressure inside the buoys is controlled by a valve which is responsive to the hydro-static pressure in the body of water or the volume of the buoy to maintain a relatively small pressure differential between the pressure inside the buoy and the hydro-static pressure at all depths of submersion whether the amount of buoyancy provided by the buoys is to be positive, negative, or neutral. Also disclosed are a plurality of systems utilizing the submersible buoys of this invention for laying pipe line and other objects on or near the sea bottom.

Abstract: A hollow generally circular horizontal float body is provided. The body tapers in thickness from its central portion of its outer periphery and includes upper and lower walls which are inclined downwardly and upwardly, respectively, from the central portion to the outer periphery of the body. A horizontal work platform is spaced above the body and supported therefrom by upstanding supports extending and secured between the body and the platform at points spaced about the central portion of the body. The body includes a central vertical passage therethrough and the interior of the body spaced outwardly of and about the central portion includes structure defining ballast tanks which may be selectively flooded and evacuated of water.