South Korean oil refiners, led by top player SK Innovation Co., logged decent earnings in the first quarter of the year on the back of robust petrochemical business, and expect their bottom line to remain firm under the current quarter thanks to the recovery of their refining margin, industry sources said Sunday.

SK Innovation posted a net profit of 859 billion won ($757 million) in the first quarter, sharply up from 566 billion won profit a year earlier, thanks to better-than-expected results from its petrochemical business.

"The petrochemicals business posted record earnings, and non-oil business also helped jack up our overall operating income," it said.

Its petrochemicals and lubricant business accounted for 55 percent of its total operating income in the first quarter, sharply up from 28 percent tallied in 2011.

Refining margins are expected to be sound for the second quarter ahead of the driving season, SK Innovation said earlier expecting solid gasoline demand under the current quarter.

GS Caltex Corp., the No. 2 refiner in South Korea, reported that its first-quarter earnings more than doubled from a year earlier aided by robust results from its petrochemicals and lubricant businesses.

Net profit reached 563 billion won in the January-March period, up 160 percent from a year earlier, The stellar performance was also driven by sound results from its petrochemicals and lubricant sectors.

S-Oil Corp., the No. 3 player, suffered a 10.8 percent fall in its bottom line from a year earlier, as the strong local currency offset its sound refining margins and widening spreads for chemicals goods.

Local refiners' earnings were mostly aided by a bullish chemicals business.

In the three month period, their petroleum exports reached an all-time high on solid demand and higher oil prices.

The country's four major oil refiners, including the smallest Hyundai Oilbank Co., exported 117 million barrels worth of oil and petrochemical goods in the first quarter of the year, up 6.5 percent from a year earlier, according to industry data.

In terms of volume, the tally marks the highest for any first quarter, they showed.

Analysts said demand for gasoline may strengthen as the global economy is showing signs of a recovery and their product margins will be good on the back of tight supply.

Refining margins will stay firm this year, in part due to solid demand for oil from Asian countries, and demand for power generation will also remain solid.

US refiners are expected to conduct large-scale maintenance work this year, according to analysts. Lee Dong-wook, an analyst at Kiwoom Securities, said local players will benefit from firm demand amid tight supply.

Refiners in South Korea racked up record earnings last year largely due to improved cracking margins, inventory gains and solid demand for petrochemical products.

The country's four major oil refiners logged a combined operating income of 8.03 trillion won last year, an all-time high figure. (Yonhap)