ABUJA, Dec 15 (Reuters) - Nigeria will clear unpaid bills worth $5.1 billion for oil production joint ventures piled up over many years under a deal signed on Thursday with Shell (RDSa.L) , Chevron (CVX.N) , Total (TOTF.PA) , Eni (ENI.MI) and Exxon Mobil (XOM.N) .

The deal would unlock new investment in the OPEC member country, Oil Minister Emmanuel Ibe Kachikwu said in a speech at the signing ceremony, adding the repayment would take place over the coming five years.

He said the oil majors had given Nigeria a discount of $1.7 billion, lowering the original amount from $6.8 billion.

The agreement would also ensure that future Nigerian payments to production joint-ventures with oil majors would be paid in time, he told reporters after the signing.

Kachikwu also said that Forcados exports would resume soon, without giving any more precise information. The grade has been under force majeure since February after multiple attacks on the pipelines that carry it to the export terminal.