Abstract: A liner sleeve is secured within a host pipe of a bimetallic lined pipe by driving a spinning friction stir welding tool through the liner sleeve but not through the full wall thickness of the host pipe. This forms a thermo-mechanically affected welded zone in which metal of the liner sleeve is bonded with some metal of the host pipe. Relative movement between the spinning tool and the lined pipe extends the welded zone along a weld path. Where the pipe is mechanically lined, the welded zone extends along a previously unbonded outboard region that extends longitudinally from an inboard region at which the liner sleeve is bonded mechanically to the host pipe.

Abstract: A subsea buoy comprises a rigid watertight external shell extending continuously around a supporting internal structure that is sealed and fully enclosed by the shell. The shell is formed integrally and simultaneously with the internal structure by the same additive manufacturing process. The internal structure comprises cavities disposed between structural members, such as struts of a lattice or webs of a matrix. The structural members and cavities can be in a hierarchical or fractal array comprising a relatively narrow outer tier adjoining the shell and at least one relatively wide inner tier within the outer tier.

Abstract: A pad for a track-type tensioner includes an interface layer made up of a plurality of rigid elements that together define a contact face of the pad for gripping a pipeline or other elongate product supported by the tensioner in use. A substrate layer of pliant material is sandwiched between a rigid base plate and the interface layer. The flexibility of the substrate layer supports the elements of the interface layer for movement relative to each other and relative to the base plate to suit an outer shape profile of the product. For example, by virtue of pivoting or translational movement of the rigid elements relative to the base plate, the same pads can adapt to different products that have different diameters.

Abstract: A method of converting a subsea laying system of a surface vessel from a laying mode to an abandonment or recovery mode includes clamping at least one tubular sleeve in at least one clamp of the laying system. A winch wire can then run longitudinally through the or each clamped sleeve when suspending an elongate subsea element such as a pipe string during abandonment or recovery operations.

Abstract: A heated subsea pipeline includes a direct electrical heating (DEH) system that heats a central major portion of the pipeline. Supplementary heating systems extend along respective end portions of the pipeline, longitudinally outboard of the central portion heated by the DEH system. A flow of heating fluid is circulated along the end portions and may be circulated through an underwater vehicle that pumps and heats the flow.

Abstract: A method manufacturing a spacer for a pipe-in-pipe system includes mixing aerogel particles with a polymer to form a mixture in which the particles are dispersed in the polymer. The resulting mixture is moulded and the polymer is solidified to form the spacer or a component of the spacer, in which the dispersed, particles are suspended in a matrix of the solidified polymer.

Abstract: A method of sealing a hole in a wall of a hollow structure comprises providing a sealed chamber that is external to the structure and that is in fluid communication with an internal space of the structure via the hole. The structure may be a pipe-in-pipe structure and the internal space may be an annulus between outer and inner pipes. Fluid flows through the hole into or out of the chamber as the pressure and/or composition of fluid in the internal space is adjusted. Then, a plug is spun and friction-welded into the hole. The plug is inserted into the hole from within the chamber.

Abstract: A subsea installation for the production of hydrocarbons includes a flowline and a group of heating cables extending along the flowline. A star end termination effecting short-circuit connection between the heating cables of the group is located at a subsea location remote from the flowline. For example, a subsea structure or fluid conduit in fluid communication with the flowline, such as a PLET or a spool, can be interposed between the termination and the flowline. The termination may be a module that is connectable electrically to the heating cables via flying leads and connector hubs.

Abstract: A method of joining together liner sections within a polymer-lined pipe energises an induction coil inside the pipe to spot-heat part of a circumferential interface between the liner sections. This melts and fuses the polymer material locally. The induction coil is then moved along the interface to heat other parts of the interface successively above the melting temperature. An apparatus for performing the method has a power supply for energising the induction coil and a drive system for moving the energised induction coil relative to a body of the apparatus. The apparatus may be configured as a carriage that is movable along the pipe.

Abstract: A method of joining together liner sections within a polymer-lined pipe energises an induction coil inside the pipe to spot-heat part of a circumferential interface between the liner sections. This melts and fuses the polymer material locally. The induction coil is then moved along the interface to heat other parts of the interface successively above the melting temperature. An apparatus for performing the method has a power supply for energising the induction coil and a drive system for moving the energised induction coil relative to a body of the apparatus. The apparatus may be configured as a carriage that is movable along the pipe.

Abstract: A method and apparatus for bending a pipe to mitigate internal wrinkling, with particular benefit when bending a lined pipe upon spooling. Bending is performed continuously by advancing the pipe through a bending zone while an internal mandrel is held at the bending zone to resist wrinkling. In one variant, the mandrel comprises longitudinally-spaced pipe-engaging elements and a tensile link between the elements allows relative movement between the elements. A holdback connection on one of the elements applies hold-back force to that element to be transmitted to the other element via the tensile link. In another variant, the mandrel comprises an elongate pipe-engaging body with a hold-back connection at one end of the body. The body is flexible to bend with the pipe and is shaped to engage an inner surface of the pipe along most of the length of the body.

Abstract: A method of providing buoyancy to a subsea structure such as a pipeline bundle includes attaching to the structure a rigid elongate buoyancy tube that defines a floodable envelope. The envelope is arranged to contain a mass of buoyant macrospheres. Multiple openings penetrate a tubular wall of the buoyancy tube, in fluid communication with a void that extends between the macrospheres inside the tube. The void floods via the openings when the buoyancy tube is submerged, whereupon the macrospheres apply buoyant upthrust to the surrounding buoyancy tube and hence to the subsea structure to which the tube is rigidly attached.

Abstract: A pipe-in-pipe section comprises an inner pipe spaced within an outer pipe to define an annulus between the inner and outer pipes. The annulus contains a solid insulating material, which may be a microporous aerogel, and an inert gas such as krypton at near-atmospheric pressure.

Abstract: A method of sealing a hole in a wall of a hollow structure comprises providing a sealed chamber that is external to the structure and that is in fluid communication with an internal space of the structure via the hole. The structure may be a pipe-in-pipe structure and the internal space may be an annulus between outer and inner pipes. Fluid flows through the hole into or out of the chamber as the pressure and/or composition of fluid in the internal space is adjusted. Then, a plug is spun and friction-welded into the hole. The plug is inserted into the hole from within the chamber.

Abstract: A pipeline bundle for a riser tower or tie-back is manufactured offshore by suspending the bundle from an installation vessel, adding structural core sections successively to an upper end of the suspended bundle, lowering the bundle after adding each successive core section, and feeding one or more lengths of flowline pipe beside the core sections for incorporation into the bundle. The flowline pipe is coiled on a reel or carousel as a full-length piece before being uncoiled progressively as core sections are added to the lengthening bundle. The flowline pipe is then engaged with guide frames and/or buoyancy blocks supported by the core sections, by movement in a radially-inward direction through a radially-outer opening in a retainer formation. The opening is then closed to hold the flowline pipe in the retainer formation.

Abstract: A weld is formed in a workpiece such as a pipeline by first activating a melting device, such as a laser, to form a molten weld pool in the workpiece and then activating a welding device, such as a GMAW torch, to initiate a weld in the weld pool. The weld therefore incorporates the weld pool homogeneously. Relative movement between the activated welding device and the workpiece continues and completes the weld while the melting device remains deactivated.

Abstract: A subsea manifold layout interconnects subsea pipelines that extend beside each other to convey hydrocarbon production fluids in use. Each of the pipelines has an in-line manifold portion that is apt to be installed with the pipeline as an in-line accessory structure lowered with the pipeline from the surface, for example using S-lay, J-lay or reel-lay techniques. Thus, the in-line manifold portions of the respective pipelines are structurally separate from each other. Bridging pipes complete a subsea manifold structure having two or more of the in-line manifold portions, providing for production fluids to flow between the pipelines via the manifold portions of the respective pipelines.

Abstract: A buoyant element for conferring buoyancy on a subsea structure or apparatus has a floodable envelope that contains a mass of buoyant spheres and a void extending between the spheres. Openings penetrate the envelope, in fluid communication with the void. One or more one destruction devices are arranged to destroy at least one of the spheres within the envelope in use. After the envelope has been submerged and flooded to fill the void between the spheres with water, the destruction devices are imploded to create shockwaves that expand the void by sympathetic implosion of the spheres. Additional water is admitted into the envelope through the openings to fill the expanding void, thereby ballasting the buoyant element.

Abstract: A method of filling a chamber with buoyant macrospheres places a mass of the spheres into a mould cavity. In the mould cavity, packing of the spheres is optimized to form an optimally-packed mass, followed by fixing the spheres in the optimally-packed mass to form a block. The block is then transferred from the mould cavity into the chamber while the spheres of the block remain fixed in the optimally-packed mass. This method enables the production of a buoyant element comprising an envelope defining an internal chamber that contains a mass of buoyant macrospheres each with an external diameter of at least 5 mm, packed with a packing factor of at least 50%.

Abstract: A mooring system has a pre-existing subsea foundation at a first seabed location and a catenary mooring line connected to the pre-existing foundation and extending to a moored floating unit. A supplementary subsea foundation is installed at a second seabed location to upgrade the capacity of the mooring system. The mooring line is connected to the supplementary subsea foundation while the connection between the mooring line and the pre-existing subsea foundation is maintained.