Abstract: A method and apparatus for buoyancy distribution along a substantially vertical submarine structure (100), the structure being provided with multiple modules (110), slidably mounted to the structure such that when vertically deployed at sea the modules are may adjust their positions along the structure by sliding, the force of each module acting upon the module above it rather than locally along the structure, resulting in the cumulative force (460) from the modules acting substantially against the top of the structure. Forces between modules may be evenly distributed by use of compliant intermediaries (310).

Abstract: The invention provides a marine riser apparatus (1) for use in the production of hydrocarbons from offshore wells and an associated method of installation of the apparatus at sea. The riser tower comprises rigid pipelines arranged in a riser tower bundle (2) and extending from a wellhead on the seabed (4) to a point below the sea surface where they are connected to flexible jumpers (3) which extend from the tower structure to connect the tower structure to a surface vessel or platform (5). The riser apparatus further comprises a buoyancy device (7) attached to the riser tower bundle, such that the buoyancy device is located above and exerts a buoyancy force on the riser tower, the buoyancy module also supporting an intermediate section of at least one of the jumpers.

Abstract: An elongate article (100) such as a prefabricated pipeline of several kilometers length is towed through water. The article is provided along its length with buoyancy adjusting material (102) fitted closely to the article. The buoyancy adjusting material is sufficient to give the article overall a positive buoyancy so that it will not sink to the seabed, and is distributed unevenly along the length of the article so as to create regions of negative buoyancy. This causes the article to adopt a wave profile with peaks (+) and troughs (?) along its length. The article is connected at its extremities to lead and trail tugs (104, 106) for controlling movement of the article through the water. Intermediate peaks are optionally coupled to intermediate tugs (108) or buoys (702) via self-adjusting ballast chains (110). The wave profile allows the towed structure to extend without undue tension on the article itself.

Abstract: Apparatus for the connection and/or disconnection of a marine riser to a floating vessel comprising, in a main embodiment, a plurality of connecting lines. The, lower ends of these connecting lines are attached to the riser and are arranged to be moveable between a first helical configuration which allows connection, via a turret, between the riser and the floating vessel and a second helical configuration wherein said connecting line is disconnected and. retracted from said floating vessel. A method of installing said connecting lines is also disclosed.

Abstract: A method of controlling the heat transfer properties of a sub-sea conduit having inner and outer walls (800, 802) and a gas-permeable space (804) between the walls providing thermal insulation, the method comprising varying the pressure of a gas within the space between values above and below a critical pressure range at which thermal conductivity of the gas exhibits a high rate of change.