Korea National Oil Corporation (KNOC) has taken control of Scottish company Dana Petroleum in a hostile takeover.
Dana's management had initially rejected the takeover approach from KNOC, but the Korean company then put the offer directly to shareholders.
KNOC said it succeeded in buying up 64% of the shares.
Dana's board has now accepted that KNOC has a controlling stake, and has advised the remaining shareholders to accept the offer.
It values the company at around $2.6bn (£1.7bn).
The company's management said Dana was worth far more, according to independent valuers but KNOC refused to lift its offer and no higher bid emerged from other quarters.
South Korea has given the KNOC a $6.5bn war chest this year to secure energy supplies.