Kazakhstan has finalized an agreement to buy a 10-percent stake in the giant Karachaganak oil and gas field.
The agreement was signed between Astana and the international consortium developing the field in northwestern Kazakhstan.
Astana's interest in Karachaganak will be run by state energy company Kazmunaigas.
Britain's BG Group and Italy's Eni own 29.25 percent of the project each. Other partners are Chevron with an 18 percent stake and Russia's LUKOIL with 13.5 percent.
BG said Kazakhstan paid $2 billion in cash and is liable for a further $1 billion noncash payment to obtain its 10 percent of the project.
Karachaganak is estimated to hold some 1.2 billion tons in oil reserves and 1.35 trillion cubic meters of natural gas.
Based on reporting by AP