Genel Energy has downgraded estimated reserves from its assets in Iraq.
The company, run by former BP boss Tony Hayward, said gross proved plus probable reserves have been estimated at 543.0 million barrels, down from 680.3 million at the end of 2014.
This reflected production over the year, technical revisions and re-categorisation of some reserves, the company said.
Genel has launched a bond buy-back programme and said proved reserves at the Tawke oil field in Iraq have increased.
The company has launched a tender offer to buy back senior unsecured callable bonds. The offer is being done for cash management purposes and Genel said it intends to acquire a minimum of $50million of the $730million of bonds in issue.
Genel also said DNO ASA, the operator of the Tawke field, has published estimated reserves for the site.
At the end of December, proved reserves at the Tawke field have been estimated at 387.0 million barrels of oil, up 21% on the 319.9 million at the end of 2014, driven by better confidence at operator DNO on primary recovery rates at the field. Genel holds a 25% stake in the field.
Last month, Genel fell by a record in London trading after cutting the reserves estimate for its largest field by almost half.
Genel dropped as much as 41%, the biggest decline since the stock started to trade in June 2011, and was down 37% at 78.75 pence as of 12:15pm.
That wiped about £128million pounds off the company’s market value.