Statoil (NYSE: STO) may have to pay more than $1 billion to other equity owners of Nigeria’s Agbami Field after receiving an expert calculation of revised tract participations.

If implemented, the calculation would reduce Statoil’s equity interest in the field from 20.21% to 15.04%, the company said in a news release. Statoil previously initiated arbitration proceedings to set aside interim decisions made by the expert; however, the arbitration tribunal has declined to set aside the expert’s interim decisions.

Statoil said it is currently assessing its position in relation to the expert’s decision and the decision of the arbitration tribunal.

So far, the company said it has made an accrual of NOK 7.5 billion (US $867 million). Assuming the expert’s ruling is implemented, Statoil will have to compensate other equity owners at Agbami about NOK 1.6 billion (US$185 million) in addition to the accrual as of the end of third-quarter 2015, according to the release. Eventual settlement of any imbalance amount will be made over time through cash-calls issued by the unit operator.