Abstract: A method for deploying a gas storage vessel below the surface of the water comprises coupling an upper end of the gas storage vessel to a deployment apparatus positioned at the surface of the water. The gas storage vessel has a total dry weight and a lower end opposite the upper end. The gas storage vessel also includes a storage tank defining an inner region inside the tank and an exterior region outside the tank. In addition, the method comprises lowering the gas storage vessel below the surface of the water with the deployment apparatus. Further, the method comprises pumping a buoyancy control gas into the inner region of the tank. The buoyancy control gas in the inner region of the tank generates a buoyancy force acting on the gas storage vessel.

Abstract: A method for developing an offshore field comprises (a) coupling a plurality of top-tensioned risers to a first vessel at a first location. In addition, the method comprises (b) decoupling the first vessel from the plurality of top-tensioned risers after (a). Further, the method comprises (c) coupling a second vessel to the plurality of top-tensioned risers after (b) at the first location.

Abstract: A frame and system for adding buoyancy to a riser used in connection with floating platforms is provided which, in some example embodiments, includes a stem attached to multiple supports which include flanges arranged to take impact and abrasion loads off an internal buoyancy module. An air management system is also provided.

Abstract: For a spar type floating platform having risers passing vertically through the center well of a spar hull, there is provided apparatus for supporting the risers from a gimbaled table supported above the top of the spar hull. The table flexibly is supported by a plurality of non-linear springs attached to the top of the spar hull. The non-linear springs compliantly constrain the table rotationally so that the table is allowed a limited degree of rotational movement with respect to the spar hull in response to wind and current induced environmental loads. Larger capacity non-linear springs are located near the center of the table for supporting the majority of the riser tension, and smaller capacity non-linear springs are located near the perimeter of the table for controlling the rotational stiffness of the table. The riser support table comprises a grid of interconnected beams having openings therebetween through which the risers pass.

Abstract: A semisubmersible floating platform for use in marine environments. The platform comprises a truss telescopingly mounted to the platform and movable between upper and lower positions with respect to the platform. At least one riser buoyancy member is telescopingly mounted to the platform and movable between upper and lower positions with respect to the platform. For each riser buoyancy member, at least one guide is attached to the truss and adjacent the buoyancy member for guiding and laterally restraining the buoyancy member.

Abstract: A frame and system for adding buoyancy to a riser used in connection with floating platforms is provided which, in some example embodiments, includes a stem attached to multiple supports which include flanges arranged to take impact and abrasion loads off an internal buoyancy module. An air management system is also provided.

Abstract: A frame and system for adding buoyancy to a riser used in connection with floating platforms is provided which, in some example embodiments, includes a stem attached to multiple supports which include flanges arranged to take impact and abrasion loads off an internal buoyancy module. An air management system is also provided.

Abstract: There is provided a semisubmersible floating platform for use in marine environments. The platform comprises a truss telescopingly mounted to the platform and movable between upper and lower positions with respect to the platform. At least one riser buoyancy member is telescopingly mounted to the platform and movable between upper and lower positions with respect to the platform. For each riser buoyancy member, at least one guide is attached to the truss and adjacent the buoyancy member for guiding and laterally restraining the buoyancy member.

Abstract: For a spar type floating platform having risers passing vertically through the center well of a spar hull, there is provided apparatus for supporting the risers from a gimbaled table supported above the top of the spar hull. The table flexibly is supported by a plurality of non-linear springs attached to the top of the spar hull. The non-linear springs compliantly constrain the table rotationally so that the table is allowed a limited degree of rotational movement with respect to the spar hull in response to wind and current induced environmental loads. Larger capacity non-linear springs are located near the center of the table for supporting the majority of the riser tension, and smaller capacity non-linear springs are located near the perimeter of the table for controlling the rotational stiffness of the table. The riser support table comprises a grid of interconnected beams having openings therebetween through which the risers pass.

Abstract: For a spar type floating platform having risers passing vertically through the center well of a spar hull, there is provided apparatus for supporting the risers from a gimbaled table supported above the top of the spar hull. The table flexibly is supported by a plurality of non-linear springs attached to the top of the spar hull. The non-linear springs compliantly constrain the table rotationally so that the table is allowed a limited degree of rotational movement with respect to the spar hull in response to wind and current induced environmental loads. Larger capacity non-linear springs are located near the center of the table for supporting the majority of the riser tension, and smaller capacity non-linear springs are located near the perimeter of the table for controlling the rotational stiffness of the table. The riser support table comprises a grid of interconnected beams having openings therebetween through which the risers pass.

Abstract: A riser tensioning device that utilizes parallel air cans. A stem having an inner diameter larger than the outer diameter of the riser is positioned around the riser and is fastened in position at the wellhead of the riser on the offshore structure. A yoke attached to the stem supports a number of sleeves around the stem. Each sleeve receives a variable buoyancy air can. The sleeves and air cans are provided with a retainer that retains the air cans in the sleeves and transfers the vertical loads of the air cans to the sleeve. The retainer is also designed to allow the air cans to be selectively removed from their individual sleeves without the need to pull the entire riser assembly.

Abstract: A compliant offshore structure in which the primary restoring force to lateral displacement is provided by elongate flex elements. A gravity base is rigidly secured to the ocean bottom. A tower extends vertically upward from the base to a position above the ocean surface. A work deck is supported atop the tower. The tower is secured to the base by elongate flex elements which are arranged in an array surrounding the central axis of the structure. Each flex element has one end secured to the base and a second end secured to the tower. The flex elements permit the tower to pivot about its lower end, thus providing the tower and deck with a compliant response to environmental forces. The flex elements also support the tower above and free from contact with the base. This eliminates the need for a vertical load bearing joint between the tower and base.

Abstract: A flexible structural joint of "flex joint" for use in an articulated structure is disclosed. The articulated structure has a first section and a second section which are located along a longitudinal axis of the structure, the first section being subject to lateral or transverse loads. The flex joint is located between the first and second sections and accommodates lateral pivoting of the first section with respect to the second section through elastic flexing or bending of certain of its members. No moving parts are used. In a first embodiment, the flex joint consists of an elongated axial load member and at least three shear and torsion links oriented so as to lie substantially in a plane perpendicular to the longitudinal axis of the structure. Each of the links is connected at one of its ends to the first section and at its other end to the second section.

Abstract: A pile assembly adapted for use in a compliant piled tower. A plurality of drive piles are driven into the ocean floor in a symetric array about a central, substantially vertical axis. A flex pile is secured to the upper end of each drive pile and extends upward to a preselected elevation above the ocean floor. The longitudinal axes of each drive pile flex pile pair are laterally offset from one another with the flex piles also being arranged in symetric array about the central axis. A tie member is provided to restrain the flex piles from lateral motion relative to one another. The tie member serves to balance the moments established by virtue of the eccentric axes of the flex pile drive pile pairs. The use of eccentric axes in the pile assemblies simplifies driving the drive piles, permits the drive piles to be placed relatively far from one another to minimize pile group effects and permits the flex pile to be designed without being constrained by driving considerations.

Abstract: A complaint offshore platform in which the primary restoring force to lateral displacement is established by flex piles driven into the seafloor and fixedly secured to the platform legs a preselected distance above the seafloor. The platform includes a substantially rigid space-frame structure extending from the ocean bottom to a position above the ocean surface. A drilling and production deck is secured atop the space-frame structure. Shear piles extend through the base of the space-frame structure to prevent lateral displacement of the base while permitting the space-frame structure to pivot about its base. As the platform sways about its base in response to environmental forces, the flex piles establish a vertical couple at the location at which they are attached to the space frame structure. This couple resists movement of the platform away from a vertical orientation. In the preferred embodiment, the flex piles are secured to the platform at or near one-half the total height of the space-frame structure.

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: A method and apparatus for installing a pipeline riser (90) through a J-tube (40) at a spud can-founded, compliant, offshore platform (20) are disclosed. The J-tube is mounted on the platform above the maximum expected mudline (28). An upper longitudinal section (44) of the J-tube passes through guide rings (46) on the platform while a lower longitudinal section (48) is maintained free of the platform. After platform settlement, the J-tube is lowered to an elevation near the actual mudline (30). During riser installation through the J-tube, a lower end (54) of the J-tube is restrained from lateral movement by a latch (70) attached to the platform. Before production operations, the lower end is released from the latch so that flexibility of the J-tube accommodates movement of the platform.

Abstract: An adjustable two-piece rope guiding device [21, 26], particularly adaptable for use on offshore guyed tower drilling and production structures [11]. On such structures it is necessary to deflect a taut guy rope [14] into a direction that may not be precisely known, or that may vary with time. Such deflection must not damage the rope by excessive static or cyclic straining or by wearing. To minimize problems of clearance within the structure the guiding is performed in two parts: (1) a permanent deflection into a direction that satisfies the foregoing clearance requirements and (2) a variable deflection occurring beyond clearance problems that completes the required total deflection.