Gulf Keystone Petroleum said third-party estimates show recoverable oil reserves in the Kurdish north of Iraq are at least twice as much as initially expected.

The company, which focuses predominately on acreage in the semiautonomous Kurdish region in northern Iraq, said third-party surveys were conducted in the Shaikan oil basin.

"With cumulative production to date of over 15 million barrels, the company benefits from a vastly increased dataset and a far greater understanding of the reservoir," Chief Executive Officer Jon Ferrier said in a statement.

Third-party assessments show proved reserves in the Shaikan reserve area at between 198 million to 306 million barrels, 55 percent more than originally estimated. Proved plus probable reserves increased by 114 percent to as much as 639 million barrels.

The proved reserve estimate is higher than the original estimate of proved plus probable reserves for Shaikan.

The company said it now has "certainty" that it can develop the reservoir with fewer wells and less capital expense per barrel of oil produced.

"Today's announcement is a further independent endorsement of the caliber of Shaikan as a world-class field," Ferrier said.

The company in July said "market constraints" meant it had to lower its production expectations from Kurdish assets.

In early 2015, the company suspended crude oil exports through Turkey and directed sales to the local market because of a lack of payment from the Kurdish government.