The lower production would wipe out more than a quarter of the year's global copper surplus, estimated at 221,000 tonnes by analysts polled by Reuters, supporting metal prices that are down almost 9 percent so far this year.
In January, BHP said it expects the Olympic Dam mine to yield some 180,000 tonnes of copper in fiscal 2015, with maintenance work scheduled for September.
But electrical failure in the milling process last month prompted BHP to bring forward regular maintenance work to coincide with repairs to the mill over the next six months, the company said.
The majority of the lost production will occur in the current fiscal year ending June 30, BHP said, adding it expects the mine to return to full production by the end of September.