Australian firm Karoon Energy has signed an agreement with Brazilian oil company Petróleo Brasileiro (Petrobras) to amend the payment terms of their previously announced $665m deal for the former’s acquisition of the Baúna field.

The Baúna field is located in the Santos Basin off the coast of the Brazilian state of São Paulo.

Karoon Energy’s wholly owned subsidiary Karoon Petróleo e Gás has signed a binding agreement with Petrobras to split the $665m consideration into two instalments.

The first instalment is a $380m firm payment of which Karoon has already paid $49.9m, and $150m is to be paid at the closing of the transaction. The remaining amount will be paid in 18 months after the closing of the deal.

Meanwhile, the second is a contingent instalment of $285m to be paid by Karoon Energy until 2026.

The Baúna field, which comprises Baúna and Piracaba oil reservoirs, has been in production since 2013 and has a current production output of nearly 16,000 barrels of oil per day (bopd) via the Cidade de Itajaí floating production storage and offloading (FPSO) platform.

Karoon Energy managing director Robert Hosking said: “Despite the changed environment, this revised agreement delivers the benefits we always wanted from acquiring a producing asset, including immediate cash flow, reasonable terms, management of risk, and opportunity for the future.

“Karoon has assessed several opportunities as part of its broad-ranging strategic review and this revised deal for Baúna has proven the best outcome for shareholders on an overall valuation and returns basis.

“Karoon is always looking to create value wherever it can be found for its investors and we will continue to work towards delivering Karoon’s operational plan to expand its production footprint in Baúna and surrounds, including Neon.”

Last July, Petrobras signed two contracts for the sale of shallow-water oilfields in Campos and Santos Basins for $1.5bn.