Noble said continued reservoir analysis and resource development prompted it to raise the reserve estimate at Tamar from 9 trillion cubic feet to 10 trillion cubic feet.
The company, which has headquarters in Houston, said it has all aspects of the project online. It's producing around 300 million cubic feet of gas, a level that could increase throughout the year.
Noble Energy Chairman Charles Davidson praised efforts that meant it took just more than four years from discovery to get the project to the operational phase.
"Building on this success, we are working with the government and our partners to sanction the next phase of development at Tamar and the domestic phase of Leviathan," he said in a statement.
Noble partner Delek Drilling said it's developing a balanced approach to the Tamar and Leviathan gas fields, which have a combined natural gas resource base of around 33 trillion cubic feet. Delek says the fields, mostly in Israeli territory, combined are the largest natural gas finds made since 2000.
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