Toll, which will operate the base on a 4.5 hectare site at Darwin's East Arm industrial precinct, is building it.

The base is expected to be fully operational by early 2015.

It will remotely support the Inpex-operated Ichthys LNG projects major offshore facilities in the Ichthys field about 820km southwest of Darwin in the Browse Basin.

Inpex director corporate coordination Hitoshi Okawa said the facilities would play a crucial role in supporting the Ichthys LNG project's offshore operations.

"Our central processing facility and floating production, storage and offloading vessel will be two of the biggest pieces of infrastructure in the oil and gas industry," Okawa said.

"With an operational life of at least 40 years - without docking - a base that can provide the maintenance, store critical spare parts for these facilities, while also supporting brownfield work is vital to our success."

Northern Territory Chief Minister Adam Giles said it was encouraging to see the likes of Toll and Inpex investing in the territory.

"Not only will this supply base create up to 120,000 man-hours of employment during construction and up to 20 permanent jobs once completed, but it will also create flow-on employment for all of the services that will support the base," he said.

"As part of our push for Northern Australia development, the government is working to establish the territory as a central support base for the offshore LNG industry.

"This project is an important step in that direction."