The loss, slightly reduced from the $20m deficit for 2012, was announced as Petroceltic revealed it had conducted a $100m (£59.7m) share placing to finance its portfolio and new ventures.
Petroceltic chairman Robert Adair, founder and chairman of Melrose, said: "While the group has made great progress during 2013 and met its production guidance under challenging circumstances, there have also been some areas of disappointment.
"Most notably these were on the exploration front, with three wells failing to encounter commercial hydrocarbons in Bulgaria, Romania and Egypt.
"Despite this, I firmly believe that our recently expanded exploration portfolio, with five new licences secured in Egypt, Italy and Greece, has the potential to deliver material resource additions."
He noted that 2013 was challenging for the wider oil and gas industry with the majority of UK-listed firms suffering share price declines.
But he added: "A number of recent merger and acquisition announcements suggest that a more positive investor sentiment is beginning to return to the sector."