Chinese energy firm Sinopec is demanding around $5.5 billion (4.9 billion euros) in arbitration from Spanish energy giant Repsol over a North Sea oil and gas fields joint venture, Repsol said Friday.

Sinopec and its British subsidiary Addax Petroleum UK are demanding the reimbursement of their investment in the loss-making joint venture called Talisman Sinopec Energy UK (TSEUK), Repsol said in a statement.

The company said the arbitration notice is "unfounded" and has little chance of success.

TSEUK was founded in 2012 with Canada's Talisman Energy, which was later bought by Repsol.

As part of the joint venture Talisman Energy sold 49 percent of its assets in the North Sea to Sinopec for $1.5 billion.

Repsol posted a loss of 1.2 billion euros last year while Sinopec say its net profit plunge by 30 percent to 32.4 billion yuan ($5.0 billion).

Energy firms around the world have taken a heavy hit in recent months as the price of crude plunges owing to a global supply glut and overproduction.