Oil and gas explorer Woodside Petroleum said it started producing oil from the $1.9 billion Greater Enfield project off western Australia on Sunday.
Reuters reported last month that commissioning activities at the field had started.
Production from the Greater Enfield reservoirs would make an important contribution to Woodside's targeted annual production of about 100 million barrels of oil equivalent in 2020, Woodside said in a statement released on Monday.
Chief Executive Officer Peter Coleman said the first oil from Greater Enfield was produced under the project's budgeted cost.
Woodside operates the Greater Enfield project with a 60% stake, while Mitsui E&P Australia Pty Ltd, a unit of Japanese trading house Mitsui & Co, holds the remainder.
Approved in 2016, the project was to develop the Laverda Canyon, Norton over Laverda and Cimatti oil accumulations and tie the new production back to the Ngujima-Yin floating production storage and offloading vessel (FPSO).
Production at the Vincent field, located 50 km (30 miles) offshore Exmouth, Western Australia, had been suspended since May 2018 so that the Ngujima-Yin FPSO could be modified to accommodate output from Greater Enfield.
Mitsui said in a separate statement that it is looking for opportunities to expand production and will continue to carry out exploration and evaluation of undeveloped reservoirs inside and outside the project permit area.
Vincent crude from the project is to be marketed jointly by a Mitsui unit, Mitsui & Co. Energy Trading Singapore Pte Ltd., and Woodside.
"Demand for low-sulphur crude oil produced through the project is expected to rise as tightening environmental regulations on marine fuels motivate the shipping industry to lower the sulphur content in fuels," Mitsui said.
(Reporting by Florence Tan, Sonali Paul and Nikhil Kurian Nainan; editing by Richard Pullin)