Behind the project: APM’s 2025 Overall Project of the Year

BP’s Greater Tortue Ahmeyim (GTA) Phase 1 project off the coast of Africa is a case study in engineering innovation, complex stakeholder management and international collaboration.

In 2015, a huge gas field was discovered lying across the maritime border of Mauritania and Senegal. A decade later, the GTA liquefied natural gas (LNG) project achieved first gas to its floating LNG (FLNG) facility, marking a new era in energy production for the region – and the successful delivery of an incredibly ambitious project by the team at BP and its partners.

Executed over six years, and with a multibillion‑dollar budget, GTA Phase 1 has been designated a national project of strategic importance by the presidents of both of its host countries. It was also named Overall Project of the Year and Engineering, Construction and Infrastructure Project of the Year at the APM Project Management Awards 2025.

A feat of engineering

The project effectively combines several megaprojects into one. Each is an engineering feat in itself. GTA Phase 1 boasts an ultra‑deepwater subsea system that includes four gas production wells, in water depths of up to 2,850m, making it one of the deepest subsea infrastructures in Africa. The extracted gas flows along an 80km‑long pipeline to a mid‑water floating production, storage and offloading (FPSO) vessel, which removes water, condensate and impurities from around 500 million standard cubic feet of gas per day. Closer to the coast, there’s a 1.2km artificial breakwater comprising 21 caissons – each the size of the Arc de Triomphe.

Behind that sits an FLNG facility ready to cryogenically cool, store and liquefy the gas before it’s transferred to carriers for export. Steve Murray, Engineering Manager at BP, describes the enormity of the engineering challenge.

“Constructing any fixed structure offshore, where nature is at its most extreme, is never straightforward, and the GTA Hub was no exception,” he says. “The artificial breakwater is positioned off a highly active coastline, which resulted in a process of technical iteration and refinement as we fought to balance the variables. We used basin tests, computational fluid dynamics, metocean modelling, cooling recirculation studies and dynamic mooring assessments to deliver an overall system design. Precision was paramount, especially as the project pushed the boundaries of industry knowledge and experience.”

This was never more obvious than when the FLNG arrived at site. The vessel was ready to be moored when the team noted a tolerance issue with the mooring line dampeners.

“In the tense hours and days that followed, the team worked swiftly to reconfigure the berthing position,” says Murray. “It was a moment that underscored the importance of adaptability and resilience, with the team using strong data to make informed and timely decisions.”

A project with global reach

In Mauritania, 28km of new roads were built to move materials to the port, which was dredged to accommodate large vessels for the project. A rock quarry in the country provided more than two million tonnes of rock for the breakwater foundation. In Senegal, 120,000m2 of land was reclaimed from the sea to create the caisson fabrication yard.

If all of this already sounds like an enormous undertaking, bear in mind that Mauritania and Senegal were completely new territories for BP prior to the project. The company had to set up everything from local offices and yards to supply chains, completely from scratch. But the work wasn’t merely a local affair. This was a global construction effort, with delivery teams that were geographically dispersed and culturally diverse. The FPSO was built at a shipyard in China, using more than 81,000 tonnes of steel, 37km of pipe spools and 1,520km of cable. The FLNG facility was converted from an existing LNG carrier at a shipyard in Singapore.

Beneath the water, things were equally complex, involving not just some of BP’s deepest water wells, but also Pioneering Spirit, the world’s largest vessel, which was brought in to lay pipes. It was an extensive, complex installation with a lead time of just five months between contract award and the arrival of the vessel in field, further complicated by takeover of the work from the existing contractor mid‑project. The pipes were laid using bespoke engineering and fabrication (via an aft‑mounted portal frame).

At its peak, the project called on 150 project professionals at BP. “It’s a source of great pride for them to have been part of what has been achieved,” said BP’s Project Manager, Integration, James Thompson. “And as the project has ramped down, it proved to be a great exporter of talent back to BP’s projects organisation.”

If GTA Phase 1 was a Herculean effort of engineering ingenuity and muscle, the results are worth it. The GTA field stretches across 33,000km2 and boasts an estimated 400 billion cubic metres of gas resources in the field. In its first phase, the project will yield approximately 2.4 million tonnes per year.

Gas from the project is expected to feed into global energy needs – with some allocated to help meet growing energy demand in the two host countries when they are ready to receive it – diversifying gas export markets and sating the world’s increased need for new sources of energy.

“Africa’s significance in the global energy system is growing, and these nations now have enhanced roles to play,” said Gordon Birrell, Executive Vice President of Production and Operations at BP.

Read more in the winter 2025 issue of Project journal

 

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