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.

A method for installing an accessory onto a pipeline to be laid on the seabed, includes launching the pipeline from a first position of a tower in which the tower is at an angle α with respect to the vertical; stopping the launch of the pipeline, and hanging off the launched pipeline in a hang off module; positioning an accessory in a tower firing line; attaching the accessory to the launched pipeline in the hang off module and to at least one A&R cable; suspending the accessory and the launched pipeline from an A&R system; disengaging the hang off module from the launched pipeline; pivoting the pipeline launch tower to an accessory launch position in which the tower is at an angle γ that differs substantially from angle α, such that a pipeline launch trajectory is created which is large enough to launch the accessory and the launched pipeline with the A&R system.

A vessel for laying a pipeline includes a plurality of workstations disposed along a pipelaying path that includes an upstream portion away from a first end of the vessel and a plurality of ramps, includes a first ramp and a downstream second ramp disposed along the pipelaying path, in the region of the first end of the vessel. Each of the plurality of ramps has a first upstream end, a second downstream end, and an adjustable inclination. The downstream end of the first ramp is positioned inboard of the first end of the vessel and above the bottom of the vessel and the upstream end of the second ramp is positioned inboard of the first end of the vessel and above the bottom of the vessel. An external ramp assembly includes ramps that can be pivoted relative to one another and locked in a selected position.

A laying tower for laying pipelines on the bed of a body of water has a supporting structure extending along a longitudinal axis and provided with guides parallel to the longitudinal axis; a first clamp, which is mounted on the supporting structure and configured for selectively clamping and releasing the pipeline in a given point along the longitudinal axis; and a second clamp, which is selectively movable along a path, which extends along a first section above the first clamp; and a second section below the first clamp and, partly, below the supporting structure and configured for selectively clamping and releasing the pipeline along the path.

The present invention provides a nonresident system for depressurizing subsea apparatus and lines comprising a depressurizing tool (5) adapted for being coupled to an ROV interface (6) of a subsea apparatus, wherein the depressurizing tool (5) is coupled to an ROV (4), wherein: the ROV interface (6) comprises a first pipeline (6a) for connection to a first hydrocarbon transport line (8), a second pipeline (6b) for connection to second hydrocarbon transport line (9), and a connection mandrel (6d); and the depressurizing tool (5) comprises a suction line (5a) adapted for being connected to the first pipeline (6a) for connection to the first hydrocarbon transport line; a discharge line (5b) adapted for being connected to the second pipeline (6b) for connection to the second hydrocarbon transport line; a pump (5c); and a connector (5d) adapted for being connected to the connection mandrel (6d) of the ROV interface (6). A method is also provided for depressurizing subsea apparatus and lines, comprising the steps of: removing a blind cap (15) from an ROV interface (6) with aid of an ROV (4); coupling a depressurizing tool (5) to the ROV interface (6) of a subsea apparatus (10); suction and removal of fluid from a first hydrocarbon transport line, wherein the first hydrocarbon transport line comprises hydrate formation; and pressurizing and reinjecting the fluid into a second hydrocarbon transport line.

A method of installing a subsea pipeline supports at least one elongate pipe stalk at the surface of the sea at a first, relatively shallow-water location by virtue of buoyancy added to the pipe stalk. The pipe stalk is then towed at the surface to a second location that is in deeper water. There, with the pipe stalk supported between leading and trailing towing vessels, at least some of the added buoyancy is removed. This causes the pipe stalk to hang with catenary curvature beneath the surface between the vessels. The catenary-curved pipe stalk hanging between the vessels is then towed to a third location for subsea installation, which may involve upending the pipe stalk before landing a lower end portion of it on the seabed.

A method of installing a subsea pipeline supports at least one elongate pipe stalk at the surface of the sea at a first, relatively shallow-water location by virtue of buoyancy added to the pipe stalk. The pipe stalk is then towed at the surface to a second location that is in deeper water. There, with the pipe stalk supported between leading and trailing towing vessels, at least some of the added buoyancy is removed. This causes the pipe stalk to hang with catenary curvature beneath the surface between the vessels. The catenary-curved pipe stalk hanging between the vessels is then towed to a third location for subsea installation, which may involve upending the pipe stalk before landing a lower end portion of it on the seabed.

A system for deploying a coil of spoolable pipe from a vessel includes a first tower configured to move longitudinally and transversely along a first track coupled to the vessel, a second tower configured to move longitudinally along a second track coupled to the vessel, and a coil drum assembly coupled to the first tower. The first tower is configured to insert the coil drum assembly transversely into an interior channel of the coil when the coil drum assembly is in a retracted position, the coil drum assembly is configured to support the coil when the coil drum assembly is in an extended position and rotate during deployment of the spoolable pipe, and the first tower and the second tower are configured to move the coil drum assembly vertically.

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. The sleeve protects gripping pads of the clamp from damage due to dashing with the wire and so makes it unnecessary to remove the pads in preparation for abandonment or recovery.

A system for deploying a coil of spoolable pipe from a vessel includes a first tower configured to move longitudinally and transversely along a first track coupled to the vessel, a second tower configured to move longitudinally along a second track coupled to the vessel, and a coil drum assembly coupled to the first tower. The first tower is configured to insert the coil drum assembly transversely into an interior channel of the coil when the coil drum assembly is in a retracted position, the coil drum assembly is configured to support the coil when the coil drum assembly is in an extended position and rotate during deployment of the spoolable pipe, and the first tower and the second tower are configured to move the coil drum assembly vertically.