PIPELINE SYSTEMS 

Typical deepwater subsea field development requires several subsea wells to be drilled at different water depths and locations. These wells will be connected by means of flowline and riser systems to floating production platform positioned near the field.

The main engineering interface for the pipeline design is related to:

For the interface requirement related to SPS and subsea connection, and lay vessel, please refer to the documents:

[3] “Subsea Production Systems” Offshore Reference Book.

[7] “Subsea Connections & Tie-in Methods” Offshore Reference Book.

[6] “Deepwater Installation Vessels” Offshore Reference Book.

A typical subsea pipeline is terminated at both ends with a structure, which has two main purposes: (1) initiation or lay-down head for the actual pipelay operation and (2) for future connection to subsea wells and riser system.

Such end termination structure (Figure 3.1, “In-Line Assembly (Total Dalia Project)” and Figure 3.2, “Pipeline end manifold (PLEM) during installation (Deep Blue vessel, Dalia Project)”) is to be equipped with different pipe fittings such as:

Tip Click these links below for access to 3D resources: 3D Interactive Model of Flowlines structures 3D Pictures of Flowlines 3D Pictures of spools 3D Pictures of jumpers

Figure 3.1 - In-Line Assembly (Total Dalia Project)

Figure 3.2 - Pipeline end manifold (PLEM) during installation (Deep Blue vessel, Dalia Project)

The above section was presenting a connection considering a rigid pipeline section. However, connections can be performed with unbonded flexible lines.

In this case, the flexible pipe structure is terminated with end-fittings at both ends (see Figure 3.3, “Flexible pipe end fitting mounting” , Figure 3.4, “End fitting locking” and Figure 3.5, “Flexible intermediate connection at working platform”). This end-fitting provides a link between the unbonded layers of the flexible pipe structures and the connection at the production platform (as a riser), or SPS or rigid pipe PLET. The end-fitting allows the sealed connection of each layer in one flange assembly .

Figure 3.3 - Flexible pipe end fitting mounting

Figure 3.4 - End fitting locking

Figure 3.5 - Flexible intermediate connection at working platform

The subsea manifold system or the riser base, where the flowline will be connected to, must be designed and equipped with due consideration of the following additional mechanical aspects (see Figure 3.6, “Deepwater Subsea Manifold” and Figure 3.7, “Subsea Well”):

Subsea hardwares used for the diverless connection of pipelines and permanently mounted on subsea structure or landed on seabed are typically:

The following are examples of subsea hardware temporarily mounted on subsea structures in order to perform the desired tie-in:

Tip Click these links below for access to 3D resources: 3D Interactive Model of XmasTrees 3D Interactive Model of Manifolds

Figure 3.6 - Deepwater Subsea Manifold

Figure 3.7 - Subsea Well

There are three main laying techniques that could be used for installation of rigid pipelines in deep water:

Each laying method is further reviewed in document [82] with detailed descriptions of related and latest installation vessels. The deepwater pipelay operations will induce high installation loads onto the pipeline with different cumulative and residual strains which need to be addressed in the pipeline design.

Flexible pipelines and umbilicals are mainly installed using the Flex-Lay methods, which is similar to the Reel-lay method, with tensioners integrated in a laying ramp or a dedicated vertical flexible laying system

The typical dynamically positioned lay vessels are hereafter illustrated:

Figure 3.8 - Steep S-Lay Solitaire vessel (installation of pipeline in 2775 m -2007)

Figure 3.9 - J Lay semi-submersible: S7000 (24”OD Blustream Black Sea in 2150m of water depth)

Figure 3.10 - Reel-Lay vessel Seven Oceal (Campos Basin (2009) : laying in 1940 m WD)

Figure 3.11 - Pipeline installation vessel: Technip Deep Blue (2500m WD pipe lay capacity)