UPDATE 1-Australia's Oil Search cuts 2018 production forecast after PNG quake; Q1 revenue falls

* Lowers full-year production guidance to 23-26 mmboe

* Q1 revenue down 14 percent (Adds details from earnings statement)

April 17 (Reuters) - Australia’s Oil Search cut its full-year production forecast and said first-quarter revenue fell 14 percent as output from its key Papua New Guinea liquefied natural gas (PNG LNG) project fell after a major quake in the region in February.

In a statement on Tuesday, the company cut its full-year production guidance to 23-26 million barrels of oil equivalent (mmboe) from an earlier estimate of 28.5-30.5 mmboe.

January-March production fell 36.1 percent to 4.84 mmboe from 7.57 mmboe a year ago. First-quarter production from the PNG LNG Project, net to Oil Search, was 4.00 mmboe, the company said, while revenue for the quarter slipped to $295 million from $343.7 million.

In February, a magnitude 7.5 quake rocked PNG’s energy-rich interior, forcing PNG LNG project operator ExxonMobil Corp to shut down operations. Production resumed last week, about two weeks ahead of schedule.

Oil Search has a 29 percent stake in the PNG LNG project and also resumed operations at its Kutubu field in PNG earlier this month.

The company said it expects 2018 unit production costs to be in the range of $10.50-$13.50 per barrel of oil, a reflecting high proportion of fixed costs in the context of the lower production outlook. (Reporting By Susan Mathew in Bengaluru Editing by Joseph Radford and Kenneth Maxwell)