Dana, fully owned by KNOC since 2010, produces 50,000 barrels of oil per day, of which about 66 percent is produced in the North Sea.
The oil discovery at the Liberator well follows KNOC's gas discoveries in the Tolmount field in August and in the Pharos field in November, the statement said.
Last week, KNOC's chief executive, Suh Moon-kyu, told Reuters that the company would invest in exploration, in line with South Korea's move to focus on exploration as it scales down spending on overseas energy and resources development.
KNOC said in October it aimed to raise 3.1 trillion won ($2.93 billion) by 2017 from local investors, including the National Pension Service, to help fund its future overseas acquisitions.
The statement added KNOC would continue to invest in exploration projects for Dana's growth.