Abstract: A system is provided for disposal of gaseous hydrocarbons produced from an undersea well, which minimizes the gas disposal cost. The system includes a polymerization station (80) mounted on an anchored floating vessel arrangement (12), which converts the gas to a liquid hydrocarbon that is stored and then transported by a shuttle tanker (52) to a refinery. The liquified gas can be mixed with liquid hydrocarbons originally obtained from the undersea well, both in the shuttle tanker and in storage tanks on the anchored vessel arrangement. Sea water can be used to create steam for the polymerization process.

Abstract: A torque enhancer (60, FIG. 1) is provided for an offshore system wherein a turret (18) is rotatably mounted about a vertical axis (22) on a vessel hull and the turret is anchored by catenary chain devices (24), to help minimize rotation of the turret when the vessel weathervanes. The torque enhancer may include a pair of members (80, 82, FIG. 3) with horizontally-spaced inner ends (84, 86) pivotally mounted on the turret and with outer ends (90, 92) coupled to a chain device (24) to transmit horizontal components (E) of tension force that tend to turn the turret to maintain it at its initial rotational orientation with respect to the seafloor. In one system, the arms are rigid beams arranged to form an A-frame, with the outer ends of the arms supporting a guide (100) and with the chain device slidably extending through the guide and attached to the vessel half way between the inner ends of the beams. In another system, a pair of chains (122, 124, FIG.

Abstract: A fluid swivel is described, of the type that carries oil, water or natural gas at high pressure between an undersea well and a weathervaning ship, which has a seal device of increased lifetime. The seal device (56, FIG. 2 ) lies in a cavity of a first swivel part (12) and includes a rigid seal ring (62) that is slidable toward and away from a sealed surface (66). A deformable seal (60) can be backed up by the seal ring, with the seal ring sliding to close the extrusion gap (70) into which the seal could extrude when high pressure fluid enters the swivel. A pressure source (80) coupled to the cavity urges the backup part to deform radially and slide toward the sealed surface with a force that increases as the pressure of fluid in the swivel increases.

Abstract: A vessel with a rotatable turret thereon is moored in a manner that minimizes turret tilt while avoiding the need to maintain precisely concentric upper and lower turret bearings. A mooring structure (152, FIG. 7) is formed by a group of mooring lines (162, 164) such as chains, with the upper ends of the lines coupled to the vessel through a connecting apparatus (154) that comprises a group of arms (166) each connected to a corresponding one of the lines. Each arm is pivotally mounted (at 170) on the turret to hang therefrom, so the arm transmits primarily vertical forces to the turret and the turret bearing (185) has to support primarily vertical forces. Each arm carries a bearing pad (174) that presses horizontally against a vessel lower bearing ring (182) mounted directly on the vessel hull independently of the turret.

Abstract: A fluid swivel is described, of the type which includes a ring-shaped outer structure (12, FIG. 2 ) that rotates about a ring-shaped inner structure (14), and which form an annular chamber (18) between them and a pair of gap passages (24, 26) between them which are sealed by pressure seals (30, 32). The outer structure includes a body (70) forming part of the annular chamber and a seal ring (72) mounted on an end of the body and abutting one side of the pressure seal. The seal ring is axially shiftable on the end of the body, so that when the body expands radially as a result of high pressure fluid being introduced into the annular chamber, the seal ring does not have to expand a similar amount and therefore does not have to cause a large increase in the width of the extrusion gap (62) at the downstream end of the pressure seal.

Abstract: A fluid swivel, of the type that carries oil, natural gas, or other fluid between an undersea well or pipeline and a weathervaning ship, wherein the seal arrangement that prevents leakage of fluid is constructed to increase the seal lifetime and reduce the cost of the fluid swivel. The seal arrangement includes a recess (44, FIG. 2) in a first of the swivel parts and a seal assembly (46) therein which includes a pressure seal (50) and a backup ring (56). The backup ring has a dynamic side (64) lying adjacent to the portion (54) of the second swivel part that is sealed against, and has an opposite distal edge portion (72). The dynamic side of the backup ring has a tapered downstream portion (80) that is tapered at an angle A of no more than 30.degree. to the axis of rotation (16) of the fluid swivel, with the downstream edge (82) of the tapered portion lying on a downstream wall (86) of the first swivel part rather than overhanging it.

Abstract: A multiple fluid swivel arrangement is described, for connecting stationary undersea pipes to rotatable pipes on a weathervaning ship, which provides ready access to each of the fluid swivels and which minimizes the diameters of the fluid swivels and their seals and other parts. Each of the multiple fluid swivels, except for the uppermost one, includes a largely horizontal arm (40A, FIG. 2) with an inner end (38) that can pivot about a largely vertical axis (32) on a fluid swivel body (33) that is connected to a stationary pipe (12A) extending to a deep underwater location. The outer end (42) of the arm is detachably connected to one of a plurality of couplings (44A, 46A) mounted on the ship. As the ship weathervanes and the arm approaches one of the vertical stationary pipes (12B), the outer end of the arm is disconnected from a coupling (44A), the arm is pivoted until its outer end lies adjacent to a second coupling (46A), and the outer end of the arm is attached to the second coupling.

Abstract: Apparatus is described for flaring large amounts of natural gas at a location spaced from an offshore production platform. The apparatus includes a spar buoy structure (32, FIG. 1) anchored at a location on the order of 0.1 kilometer from the platform (12) and coupled through an undersea conduit (44) to the platform. The structure is anchored by catenary chains (71-74), and has a ballasted lower portion and a buoyant upper portion to keep the structure upright so the flare (42) always remains high above sea level. The undersea conduit (44) which carries natural gas to the structure, connects to a buoy pipe (66) that extends along the structure, at a location (64) close to the center of gravity (80) of the structure, or at the bottom (keel) of the buoy, to minimize failure from constant structure pivoting. A wide lower part (34) of the structure includes several individually-sealed air-filled chambers (91-98, FIG. 2) spaced along its height. A mechanism (100, FIG.

Abstract: A mooring terminal for deep water mooring is provided having a mooring head to which ships can be attached while either receiving or unloading liquid products. The mooring head is constructed so that it can accommodate all motions of the ship and includes a pair of yoke arms carrying hoses external from the mooring head to the ship. The yoke arms are attached to the mooring head in a manner to be able to pivot about a horizontal axis. The mooring head is supported above a deck which can rotate about a vertical axis in a manner to be rotatable about an axis orthogonal to the axis about which the yoke arms rotate. A pipe extends through the tower and at the top is coupled to the hoses by means which are pivotable about the same axes as the mooring head.

Abstract: A mooring and cargo handling system for difficult-to-handle cargo such as liquified natural gas (LNG), is provided, which includes a swivel unit mounted on a mooring station and having rotatably connected sections respectfully coupled to a shore installation and to a ship that is moored to the mooring station. The swivel unit sections are connected by a rotary bearing and rotary outer seal, and the unit has a wall forming an auxiliary chamber extending along the bearing and seal, so that evaporating LNG must pass through the auxiliary chamber before it can escape through the bearing and outer seal. A gas pipe connects the auxiliary chamber to the ship or the shore installation where the evaporated gas can be flared or reliquified.

Abstract: An offshore mooring terminal or buoy is provided with apparatus for indicating to a ship moored thereto that the stresses on the mooring equipment of the buoy reached a dangerous level and the ship should cast off in order to avoid serious damage to the buoy, possibly to the ship and also to avoid a possible cargo spill.