Norwegian investment firm Aker will consider options for its stake in oil startup Aker Energy after the unit has appraised its offshore field in Ghana and submitted a development plan for the site to the Ghanaian government.

Aker Energy bought a 50-percent stake in Ghana's ultra deepwater Tano Cape Three Points block from Hess for $100 million in February.

Options for the stake include listing Aker Energy separately, offering it for sale to oil companies in the area or those seeking to enter Ghana, or a combination of both, Aker's CEO Oeyvind Eriksen told Reuters.

Aker Energy is 50 percent owned by Aker, an investment vehicle of Norwegian billionaire Kjell Inge Roekke. His privately held vehicle TRG owns the other half.

A decision could be made within six to 12 months, Eriksen added.

Aker Energy planned to submit the field's development plan to the Ghanaian authorities in the second half of this year, he said, after drilling at least one well to appraise the resources, preliminary estimated to be in a range of 400 million barrels of oil equivalents (boe).

Roekke's TRG has a stake in a neighbouring South Deepwater Tano block, where the first exploration well is to be drilled this summer, therefore a potential combined development of the two blocks could be possible, Eriksen said.

"Ultimately the geology will define the development concept," he added.

Investment in Aker Energy has formed part of Aker's move from the oil service industry into oil exploration and production. Aker said it had no plans to invest in new oil service segments, such as drilling.

"Aker has no intention to make an investment in Maersk Drilling or other drillers," Eriksen said, addressing market talk that Roekke's company was looking at the Copenhagen-based offshore rig firm.

The value of Aker's industrial holdings increased to 44.9 billion Norwegian crowns ($5.54 billion) in the first quarter from 44.6 billion in the fourth-quarter, the company said, while the value of its oil service assets fell.


($1 = 8.1094 Norwegian crowns)

(Reporting by Nerijus Adomaitis, editing by Gwladys Fouche and Alexandra Hudson)