ALGIERS - Algeria's state energy company Sonatrach has signed a deal with Spanish firm Cepsa to boost production at the Rhourde el Khrouf oil and gas field in southeastern Algeria, Sonatrach's chief executive said on Thursday.

The deal should raise production at the field from 11,000 barrels per day of oil to 24,000 bpd of oil after five years, and to 10,000 bpd of liquefied petroleum gas after six years, Abdelmoumen Ould Kaddour said.

The deal includes a $1.2 billion investment and the length of the contract is 25 years, he said.

"The field was about to die, but technology has allowed us to raise output. This is why partnership is key to us," Ould Kaddour told reporters at a signing event in Algiers.

Rhourde el Khrouf is about 320 km (200 miles) southeast of the giant Hassi Messaoud oilfield.

Ould Kaddour said Sonatrach had yet to decide where to invest in a refinery overseas as part of a push to reduce Algeria's fuel import bill. He had said earlier this week that Sonatrach was negotiating to buy shares in a foreign refinery, without giving details.

"We are still in the process of choosing a refinery. We have not decided yet," Ould Kaddour told Reuters on the sidelines of the event.

Sonatrach officials said on Tuesday that the firm had signed a deal with Vitol, the world's largest oil trader, to exchange crude for refined products, after its fuel import bill soared to a record $2.5 billion because of refining problems.  

(Reporting by Lamine Chikhi; Writing by Aidan Lewis; Editing by Alexander Smith and Dale Hudson) ((Aidan.Lewis@thomsonreuters.com ; +216-29850352;))