Allseas’ Pioneering Spirit has completed the infield pipelay scope for BP’s ultra-deepwater GTA liquified natural gas project offshore Mauritania and Senegal. Two months after arriving in the field, production crew welded, scanned and field joint coated the final piece of pipe for the second 16-inch export gas line.

Safely landed in a 2-metre target box at 2400-metre water depth, the pipeline will be recovered in J-mode configuration to install the termination assembly. To make this happen, the vessel aft has been fitted with a bespoke J-mode frame with a 1000-tonne load capacity. Allseas‘ engineering and fabrication teams have designed, built and installed this frame on board in only eight weeks.

The pipelay scope comprises approximately 75 km of 16-inch export lines and 10 km of 10-inch CRA infield lines, some of the pipeline infrastructure exceeding 2700 metres water depth at the deep end. To meet Allseas’ ambitious production rate, the main firing line and double jointing facilities on Pioneering Spirit have run in parallel throughout the campaign.

Also read: Allseas lands BP pipelay job for Pioneering Spirit

Pioneering Spirit will conclude the offshore works by installing the six outstanding flowline termination assemblies.

Allseas Project Manager Laurent Beghin: ‘Our agile approach was key to a quick and efficient start to the project and decision-making process throughout the offshore campaign. Thanks to great collaboration between the onshore and offshore teams, we’ve overcome all challenges faced during the project preparation and execution phases and met all milestones without delay.’

Below are some pictures of the operation.

Pioneering Spirit

Pioneering Spirit is the largest offshore construction vessel in the world. Designed completely in-house, the vessel is designed for the single-lift installation and removal of offshore platforms and the installation of record-weight pipelines.

The twin-hulled vessel is 382 metres long and 124 metres wide. At the bow is a slot, 122 metres long and 59 metres wide, that enables Pioneering Spirit to move around a platform and lift and transport entire topsides using eight sets of horizontal lifting beams.

Also read: Pioneering Spirit to install substation for French offshore wind farm

For jacket removal and installation, two 170-metre-long lifting beams, which can rotate on hinges, is located at the vessel’s stern. This Jacket lift system was deployed on the Ninian Northern jacket removal in 2022. Complementing the lifting systems is a 5000-tonne special purpose crane for additional lifts such as lighter topsides and jackets, modules and bridges.

In 2022, Pioneering Spirit surpassed the 330,000-tonne mark for lifted platform weight.

All pictures by Allseas.

South Line works (by Allseas)
South Line works (by Allseas).
South Line works 2 (by Allseas)
South Line works 2 (by Allseas).
South Line works 2 (by Allseas)
South Line works (by Allseas).
Starting up the 16-inch South Line (by Allseas)
Starting up the 16-inch South Line (by Allseas).