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 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 portion of a line from a line laying vessel to a touchdown support point on or near to the seabed is imaged with a 3 dimensional sonar imaging system to produce coordinates of a series of touchdown points using a time sequence of sonar images, and the time series of touchdown points is recorded.

A portion of a line from a line laying vessel to a touchdown support point on or near to the seabed is imaged with a 3 dimensional sonar imaging system to produce coordinates of a series of touchdown points using a time sequence of sonar images, and the time series of touchdown points is recorded.

A method of installing a subsea pipeline for tie-in to a subsea structure includes laying, using a pipe laying vessel, an intermediate section of the pipeline on to a pipe restraint device, wherein the pipe restraint device is at or near the subsea structure, or is at or near a location at which a subsea structure will be installed, and the pipe restraint device restricts transverse movement of the pipeline. The intermediate section of the pipeline is configured to be tapped at or near the pipe restraint device for providing fluid communication between the pipeline and the subsea structure.

A method of installing a subsea pipeline for tie-in to a subsea structure includes laying, using a pipe laying vessel, an intermediate section of the pipeline on to a pipe restraint device, wherein the pipe restraint device is at or near the subsea structure, or is at or near a location at which a subsea structure will be installed, and the pipe restraint device restricts transverse movement of the pipeline. The intermediate section of the pipeline is configured to be tapped at or near the pipe restraint device for providing fluid communication between the pipeline and the subsea structure.

A method of installing a subsea tie-in conduit comprises unspooling or manufacturing a steel rigid lined pipeline (14) aboard an installation vessel and launching the pipeline progressively from the vessel (10) into water. A distal end of the tie-in conduit is coupled to a proximal end of the pipeline above the surface and is then launched into the water coupled to the pipeline. The suspended weight load of the pipeline is supported by an A&R wire (34) connected to the proximal end (38) of the pipeline, defining a load path that bypasses the tie-in conduit (30). A proximal end of the tie-in conduit may be suspended from that wire. The tie-in conduit is of composite or flexible pipe, hence being pliant relative to the lined rigid pipeline and maintaining its internal corrosion resistance. After landing on the seabed, the tie-in conduit may be deflected relative to the pipeline for connection to a subsea connection point.

A method of installing a subsea tie-in conduit comprises unspooling or manufacturing a steel rigid lined pipeline (14) aboard an installation vessel and launching the pipeline progressively from the vessel (10) into water. A distal end of the tie-in conduit is coupled to a proximal end of the pipeline above the surface and is then launched into the water coupled to the pipeline. The suspended weight load of the pipeline is supported by an A&R wire (34) connected to the proximal end (38) of the pipeline, defining a load path that bypasses the tie-in conduit (30). A proximal end of the tie-in conduit may be suspended from that wire. The tie-in conduit is of composite or flexible pipe, hence being pliant relative to the lined rigid pipeline and maintaining its internal corrosion resistance. After landing on the seabed, the tie-in conduit may be deflected relative to the pipeline for connection to a subsea connection point.

A pipeline protection and leveling device for an underground pipeline. The device includes a permeable housing structure having a left side, a right side, a bottom and an open top. An excavator hook lift strap, an upright lift strap, and at least one side lift strap each extend from the permeable housing structure. A top opening closure mechanism is configured to close the open top.