Oil Search's full year profit has dropped by 13 per cent due its increased exploration activity.
The energy company has also forecast lower production and higher costs in calendar 2013.
Oil Search made a net profit of $US175.8 million ($A171.40 million) in the six months to December 31, down from $US202.5 million in the previous corresponding period.
"This was largely driven by higher exploration expense, of $US144 million ($A140.40 million) compared to $US60.6 million in 2011," managing director Peter Botten said in a statement on Tuesday.
"This reflects the company's increased level of exploration activity in 2012."
The company said its liquefied natural gas (LNG) project in Papua New Guinea was 75 per cent complete and on target for first sales in 2014.
Oil Search forecast production of 6.2 to 6.7 million barrels of oil equivalent (mmboe) in 2013, compared to 6.4mmboe in 2012.
Underlying operating costs are expected to be in a range of $US24 and $US26 per barrel of oil equivalent, compared to $US24.82 in 2012.
Exploration expenditure would be similar or slightly higher than in 2012, Oil Search said.
The company declared a final dividend of two US cents per share, unchanged from the previous year.