"The notification of the discovery follows the completion of a well testing program of the Sheikh Adi-2 exploration well on the block, located immediately to the west of the company's Shaikan block, which is a major commercial discovery," the company said in a statement.
Preliminary tests of the well yielded a flow rate of 4,235 barrels of heavy crude oil per day.
Last month, the company said ongoing work to commission two facilities in the region could lead to the production of 40,000 barrels of oil per day by the middle of next year. Full-scale production of 150,000 bpd should be reached by 2015, the company said.
In November 2011, the explorer revised the reserve estimate at its Shaikan oil discovery in Iraq up to 10.5 billion barrels.
"This most recent exploration success points to the significant potential for further growth and future synergies across our world-class acreage in the Kurdistan Region of Iraq, Gulf Keystone Chief Executive Officer Todd Kozel said in a statement.
The central government in Iraq has said it considers unilateral oil work with the semiautonomous Kurdish administration illegal.