Kazakhstan has moved its long-running conflict with several major international oil companies to a Swiss arbitration court, seeking up to $166 billion in damages over delays, rising costs, and lost revenues tied to the development of the Kashagan oilfield.

The Kashagan project—one of the world’s largest and most technically challenging offshore oil ventures—is operated by the North Caspian Project consortium. The group includes Kazakhstan’s state firm KazMunayGas with 16.88%, while ExxonMobil, Shell, Eni, Chevron, and TotalEnergies each hold 16.81%. China’s CNPC owns 8.33%, and Japan’s INPEX controls 7.56%.

Kazakhstan argues that the consortium’s delays and cost overruns significantly reduced expected income from the field, prompting the massive financial claim. In a separate case, the government is also pursuing about $15 million plus interest from Eni and other companies over alleged bribery linked to earlier development contracts. Officials hope Swiss judges will consider evidence drawn from proceedings previously held in Houston and Italy.

Eni, responding to Bloomberg, denied the allegations, noting that similar claims had been reviewed and dismissed by Italian authorities more than a decade ago. The company said a related request for documents in a Houston court was largely rejected, reinforcing its position that the accusations lack merit.

Earlier in the year, the oil companies won a legal victory in Kazakhstan when an appellate court overturned a $4.4 billion fine related to sulfur storage practices at the Kashagan site.

The new arbitration filing marks one of the largest legal challenges ever brought against international oil producers, with potential implications for both the consortium and Kazakhstan’s energy sector.