The 120 pipeline segments, each measuring 36 m in length, were welded together and pushed gradually through the 4.3 km tunnel that was drilled using a tunnel boring machine (TBM).
The 3.45 m under-sea tunnel runs 8 m below the sea bed, drilled with a 100 m long TBM weighing 277 tonnes. The operation took four weeks to complete.
Santos Vice-President downstream GLNG Rod Duke said the pipeline would soon be ready to deliver gas to Curtis Island.
Mr Duke also said the pipeline has been completed without disturbing the local environment, thanks to the TBM tunnel.
“When we set out to build a 420 km pipeline from Fairview field to Gladstone we promised to safeguard the environment,” he said.
“Our under-sea tunnel has allowed us to cross The Narrows without disturbing the local marine environment and with minimal impact to the surrounding coastal environments.
“In the coming weeks the marine crossing pipe will be connected to the rest of Santos GLNG’s 420 km pipeline.”
Subcontractor Theiss constructed the tunnel using the TBM application, while the gas transmission pipeline is being built by Santos GLNG’s contractor Saipem Australia.