Chevron in 2011 discovered huge gas fields containing an estimated 40 trillion cubic feet of natural gas off the remote northwest coast of Western Australia.
This is enough energy to power a city of 1 million people for 800 years, with cleaner, natural gas capable of meeting rapidly growing energy demands more efficiently and with less impact on the environment, according to Chevron. The company claims the facilities will be among the world’s most greenhouse gas–efficient liquefied natural gas (LNG). The Chevron-operated Gorgon Project will harness this energy, becoming Australia’s largest single resource project, incorporating its biggest subsea development and the world’s largest commercial-scale project for carbon dioxide (CO2) injection.
The project plans include a 15m-metric-ton-per-year LNG plant and a domestic gas plant to be constructed on BarrowIsland 70 km from the Greater Gorgon Area gas fields. LNG will be offloaded for transport primarily to markets in Asia, while domestic gas will be piped to the mainland.
The company plans to safely inject and permanently store about 2 trillion cubic feet of CO2 more than 2,500m beneath Barrow’s surface—four times more than any previous project. This technology will help reduce the project’s net greenhouse gases by 40 per cent, said Chevron.
The selection of Barrow Islandas the preferred site for the development presents a unique situation for the project teams. The island was declared a Class A nature reserve in 1910, and its rare native fauna and flora have been sharing their home with Australia’s largest onshore oil field for more than 45 years. Balancing the dual goals of development and conservation, the Gorgon Project will occupy just 300 hectares, or 1.3 per cent, of the island’s uncleared land mass.
Between 20 and 30 producing wells will be drilled over 30 years. Subsea trees will connect to cluster manifolds via well jumpers, all on the ocean floor. Flow lines of various sizes, managed to guard against corrosion, will connect the pipeline termination structures together and form the conduit for produced fluids to the LNG plant on BarrowIsland.
One major engineering hurdle for Chevron was the need for the pipeline to traverse the continental shelf en route to Barrow, crossing an underwater escarpment 100 to 200m high with slopes of up to 70 degrees. A thorough analysis considered two routes: the southern route, with terrain that was more benign, but added 45km to the pipeline distance, would have resulted in increased back pressure and significant costs; the northern route, which was ultimately selected, saved installation costs and improved operability because of the shorter pipeline length.