Proven reserves have been estimated at three billion barrels of oil and gas of 111 million tones of oil equivalent.

The field has proven reserves of more than two trillion cubic metres of gas and 83 million tonnes of gas condensates.

It provides 5 per cent of the world's daily production, but holds 10 per cent of proven reserves.

But proven reserves have changed hands at anything between $10 a $15 a barrel, which suggests some upside.

Proven reserves stand at about 2.5 billion barrels.