New milestone for Allseas pipelay vessel on huge gas project offshore Australia (Gallery)

Switzerland-headquartered offshore pipeline installation, heavy lift, and subsea construction contractor Allseas has tucked a new milestone under its belt for a pipeline assignment on a Santos-operated natural gas field development project off the coast of Australia.

The Federal Court of Australia granted an interim injunction on November 2, 2023, to prevent Santos from starting to lay the Barossa gas export pipeline (GEP) until November 13, 2023, due to an application made by Simon Munkara, seeking an order to make the Australian energy giant revise and resubmit the environment plan (EP) that was accepted by the regulator, NOPSEMA, in March 2020.

Based on the Federal Court of Australia’s ruling, pipelay activities were cleared to begin on an 86 km section of pipeline for the Barossa GEP, thus, Santos confirmed that no activity would occur south of kilometer point 86 (KP86). However, the court’s final decision ended up in favor of Santos in January 2024, enabling the Australian giant to continue with its planned work on the gas development project.

As a result, Allseas, which was awarded a gas export pipeline contract for the Barossa project in September 2019, has been able to make inroads on this assignment, which covers the installation of a 262-km, 26-inch carbon steel export pipeline with external anti-corrosion and concrete coating; procurement of coated line pipe; design, fabrication, and installation of two PLETs; pipeline route optimization and mattress installation at the crossing locations; pre-commissioning activities such as flooding, cleaning, gauging, and hydro-testing; and post-lay and as-built surveys.

According to the Swiss player, the Audacia pipelay vessel has installed its largest-ever PLET in S-mode, concluding several years of in-house engineering, fabrication, and testing. The company explains that due to the heaviness of the pipeline end termination structure, the production crew had to install it separately to the connector head. The width and height complicated matters further as they were such that it only barely managed to fit through the tensioners and over the stinger.

“To prepare for installing the payload, the in-house design was tested extensively last year. The hard work paid off. Offshore crew landed the PLET safely onto its mudmat foundations, installed to pinpoint accuracy earlier in the campaign by Fortitude. A great team effort,” highlighted Allseas.

The company underlines that Audacia and its support team of vessels, consisting of Fortitude, Alegria, Felicity, and Fortress are laying the 262-kilometre-long Barossa GEP. The 26-inch diameter pipeline will connect the Barossa field development to the future Darwin Pipeline Duplication, transporting natural gas to the Darwin LNG facility in Australia’s Northern Territory.
 
Commenting on the new Barossa milestone, Dennis Telders, Allseas’ Project Manager, pointed out: “To make it work, we had to come up with a design that worked in S-mode, so over the stinger, as opposed to J-mode, over the side.”

The FID for the Barossa project was taken in 2021, kick-starting the $600 million investment in the Darwin LNG life extension and pipeline tie-in projects to extend the facility life for around 20 years. This development project entails an FPSO vessel, subsea production wells, supporting subsea infrastructure, and a gas export pipeline tied into the existing Bayu-Undan to Darwin LNG pipeline.

BW Offshore has made considerable progress in constructing the FPSO BW Opal, which will be used for natural gas production from the Barossa field, thanks to a fixed 15-year FPSO contract, valued at $4.6 billion, which contains additional ten-year extension options.

The Barossa project is owned by a joint venture between Santos (operator, 50%), SK E&S (32.5%), and JERA (12.5%), The first gas is slated for the first half of 2025.