Kazakhstan is considering imposing an oil export tax on Chevron’s Tengiz field, broadening a campaign to milk more revenues from the petroleum industry.

When the $109.81 per tonne oil export duty was launched in May, Kazakhstan said big foreign oil projects shielded against adverse tax changes by contracts signed in the 1990s would be exempt. But this month KPO, the oil group led by BG and Eni developing the huge Karachaganak field, was forced to pay the duty.