Ghana's Tweneboa and Jubilee oil fields could contain up to 1.4 billion and 1.5 billion barrels of oil equivalent in oil and gas reserves respectively, said field operator Tullow Oil PLC Thursday.

This represents a slight decrease in the total resource upside estimate for Jubilee, from 1.8 billion boe previously, but no change in the figure for Tweneboa.

First oil will be produced from the Jubilee field in November or December this year and the project will be completed within 10% of its $3.2 billion budget, Tullow said in a presentation to analysts posted on its website.