The decommissioning of 21 old oil rigs in the Campos Basin, Rio de Janeiro state, will cost around 50 billion reais ($12 billion) over the next five years, a state official said.

All 21 old rigs that will be decommissioned are operated by state-controlled oil company Petroleo Brasileiro SA, development secretary Lucas Tristão told Reuters. He expects decommissioning work to generate 50,000 jobs in the state.

The decommissioning in the Campos Basin mature fields is happening simultaneously with new rigs coming into operation in the Santos Basin, where most of the Brazilian pre-salt oil is located. Some oil rigs are more than 70 years old, according to oil regulator ANP. Around 41% of offshore fields have been operating for more than 25 years.

Earlier this month, Petrobras decommissioning manager Eduardo Zacaron said the company would begin by 10 platforms through 2020, including six FPSO in the Campos Basin.

($1 = 4.1196 reais)

(Reporting by Marta Nogueira in Rio de Janeiro; editing by Grant McCool)