* Deal to be finalised in H1 2018
* Plans to expand shale oil development businesses (Adds details, background)
SEOUL, March 21 (Reuters) - SK Innovation, owner of South Korea's top refiner SK Energy, said on Wednesday that it has signed a deal to buy U.S. shale oil and gas company Longfellow Nemaha LLC in a bid to expand its shale oil development businesses.
The South Korean company said in a statement it would finalise the deal within the first half of this year but did not disclose a deal price.
SK Innovation said the acquisition was made through its U.S.-based unit SK E&P America and it would invest up to 485.3 billion won ($453 million) in SK E&P America to spend on the acquisition and other businesses, including drilling.
SK E&P America entered the U.S. shale oil market in 2014 when it acquired two oil fields in 2014, one each in Oklahoma and Texas.
Longfellow's oil assets are located in Oklahoma's STACK play, about 40 km from SK E&P America's existing Oklahoma field, the statement said. ($1 = 1,071.1000 won) (Reporting by Jane Chung; editing by Richard Pullin)