About 435 miles of pipeline connects the facilities, which include a gas conditioning plant and liquefaction and storage facilities with capacity of 6.9 million tonnes of LNG per year.
Production has been ramping up since first gas from the project left PNG bound for Japan for Tokyo Electric Power Co on the Spirit of Hela tanker in May.
"ExxonMobil PNG Limited, the operator of the PNG LNG project, confirms that the PNG LNG project facilities are now producing at full capacity and according to design," an ExxonMobil PNG spokeswoman said.
"This follows a safe ramp-up process over the last few months."
The project is expected to produce more than 9 trillion cubic feet of gas over its estimated 30 years of operations.
It will provide a long-term supply of LNG to four major customers in the Asia region including China Petroleum and Chemical Corp (Sinopec), TEPCO, Osaka Gas and CPC Corp Taiwan.
The PNG LNG project is operated by ExxonMobil PNG in co-venture with Oil Search, National Petroleum Company of PNG, Santos, JX Nippon Oil & Gas Exploration Corporation, Mineral Resources Development Company (representing landowners) and Petromin PNG Holdings.