Oslo-listed BWO is paying $49.3m for full control of the FPSO Petroleo Nautipa and a $10m working capital consideration for the shipowning company Tinworth.
The unit is on a long-term charter with Vaalco Energy in Gabon.
That firm deal runs until 2020 and included options for a further two years.
Chief financial officer Knut Saethre could not be reached for comment on the latest development today.