Covestro AG, the Bayer spinout and plastics manufacturer whose North American headquarters is in Pittsburgh, is poised to be acquired by Adnoc International for about $18 billion.

The tie-up is part of the oil producer’s big bet on chemicals, as it tries to transform into a fully integrated energy company.

The deal marks a cornerstone for ADNOC’s plans to grow its petrochemicals business along with gas and renewable energy.