MEGA GAS PROJECT OFF THE COAST OF AFRICA NEARS FINAL STAGES BEFORE START-UP

Seven years in the making, something remarkable is taking shape in the ocean where Mauritania and Senegal meet. A project, which includes a breakwater, subsea, a floating liquefied natural gas facility (FLNG), and floating production, storage and offloading vessel (FPSO) – each an engineering feat in its own right – is now in place as the finish line approaches for the development of the Greater Tortue Ahmeyim Phase 1 mega-project.

GTA Phase 1, as it’s known for short, is expected to produce up to 2.3 million tonnes of liquefied natural gas (LNG) per year, helping to meet global demand, and boosting the economies of these two developing economies.

Connecting the pieces
When complete, GTA will be operated by bp on behalf of its partners, including Kosmos Energy, PETROSEN and SMH. Here’s how the parts of this project work together to produce gas and LNG:

Subsea pipelines and infrastructure – the deepest in Africa – will feed into a floating production, storage and offloading vessel (FPSO) that will process gas delivered from wells 2,800 metres underwater, around three times the height of the world’s biggest skyscraper, the Burj Khalifa.

Constructed in China over the course of six years, the FPSO arrived at its GTA home in May 2024, 40 kilometres offshore. With this final major piece of the puzzle in place, the project can move ahead towards commissioning, start-up and first gas production.

Connected to the subsea network by flexible pipelines, the FPSO will remove water, other liquids and impurities before the gas is transferred by another pipeline to a floating liquefied natural gas vessel (FLNG), called Gimi, which is owned and operated by Golar LNG.




Located 10 kilometres offshore, Gimi is berthed at a specially-built hub terminal. This includes a 1.25-kilometre-long breakwater made up of 21 giant 16,000-tonne concrete structures, each nearly the size of the Arc de Triomphe. It was constructed to protect both Gimi and visiting LNG carriers from bad weather.

Once the gas arrives at the FLNG facility, it will be cooled to temperatures below minus 160ᵒC to transform it into liquefied natural gas. In total, Gimi is designed to produce around 2.3 million tonnes of LNG a year. Visiting LNG carriers will then take the LNG to its buyers.

An industry first
Before starting on any construction, bp teams needed to first determine the best way of working in ultra-deep water.

“Working in these water depths was a first for bp and this project is one of the deepest in the industry. This was without doubt the biggest challenge I’ve faced in my career,” says Tim Farrant, subsea engineering manager.




The project required the building of hundreds of kilometres of subsea pipelines and control systems to extract and transport the gas safely through the wells and subsea infrastructure on the seabed 120 kilometres off the coast of Mauritania and Senegal. bp’s contractors also installed fibre optic cables and structures on the seabed that then needed to be connected with the utmost precision.

The seafloor in this area of the Atlantic is so deep that robots rather than divers were used to connect the infrastructure. The pipelines also needed to be longer than on most projects, given the locations of the fields, the FPSO and the hub terminal.

“It’s been possible for us to develop this project because of the techniques and expertise we’ve developed working on projects in places like the Gulf of Mexico and the North Sea,” says Edmund Wynne-Williams, project general manager for integration. “GTA phase 1 has taken our capabilities to new limits.”