"It's been a long road from when exploration started to today, when we finally have the opportunity to sign the official agreement for the beginning of development of production of the offshore Cape Three Point project," Ghanaian President John Mahama said after the signing ceremony.
"We expect the gas will be able to produce an additional 1,100 megawatts of power for Ghana," he said.
Mahama said that the field would likely produce natural gas for the next 15 to 20 years.
"I am particularly excited about this development. We will do whatever we can to ensure this project comes on stream as soon as possible," he asserted.
The project is expected to come online in 2017.
The Ghanaian president described the deal as the single-largest investment in an African country to be made this year.
"Last year, it was anticipated that foreign direct investment in Africa would amount to some $53.3 billion," he said.
"This current agreement, signed for the investment in offshore Cape Three Point, is to the tune of $7 billion – that's about 12 percent of the total $53.3 billion," crowed Mahama.
Tiro Anthonio Magano, ENI's executive vice president, said the deal marked the beginning of a new era, when Ghana would begin producing its own gas with its own power plant, providing the country with a stable power supply.
"We were here in the early 60s to build and commission the Tema oil refinery," he recalled. "Over 50 years later, we are here again to commence a long-term project."
Vitol Chief Executive Ian Taylor, for his part, said the firm hoped to help Ghana develop.
"I am delighted that, after starting this project in 2007, it is beginning to become something," he said. "Now we have to get on and make it happen."