The April 9 letter from Energy Minister John-Peter Amewu to the two companies says seismic data indicates that Eni's Sankofa offshore field, which entered production in 2017, and Springfield's recently discovered Afina field have "identical reservoir and fluid properties".

It instructs the companies to begin within 30 days the process leading to the unitization, or joint operation, of the two fields in order to ensure efficient production and gives them 120 days to provide the ministry a draft agreement.

Spokespeople for Eni and Springfield confirmed they received the letter but declined further comment.

Amewu's letter says Eni had previously argued it was premature to be talking about unitization since Springfield had not yet appraised and tested its discovery, but that the ministry rejected that argument.

Sankofa is part of Eni's Offshore Cape Three Points project off Ghana's Atlantic Coast, which it says has reserves of about 40 billion cubic meters of unassociated gas and 500 million barrels of oil.

Springfield, a wholly owned Ghanaian company, said in December that it had discovered 1.5 billion barrels of oil and 0.7 trillion cubic feet of gas at its Afina field.