By Ron Bousso

LONDON (Reuters) - North Sea oil and gas producer Chrysaor has agreed to acquire stakes in three ageing fields from Spirit Energy, hoping to prolong their production with new drilling, the company said in a statement.

Private equity-backed Chrysaor, which last year acquired a large portfolio of assets from Royal Dutch Shell (LON:RDSa), will become the sole owner of the Armada, Maria and Seymour fields following the completion of the deal, planned for the second half of 2018.

The value of the deal was not disclosed.

"The acquisition is part of Chrysaor's strategy to prolong asset life, maximise recovery and deliver value from the UK North Sea," Chief Executive Officer Phil Kirk said in a statement.

The company will soon begin site surveys in preparation of drilling new wells in the fields, he added.

As part of the deal, Spirit, an oil and gas joint venture created last year betweenCentrica (L:CNA) and Bayerngas Norge, will retain costs linked to future decommissioning - plugging and dismantling - of the fields, the statement said.

Chrysaor is among a new generation of smaller, privately-owned companies that entered the North Sea in recent years by acquiring fields from long-standing oil companies such as Shell, Engie and OMV, hoping to extract oil at lower costs thanks to nimbler operations.

Backed by Harbour Energy, an investment vehicle of EIG Global Energy Partners, Chrysaor has stakes in 10 fields and produces around 130,000 barrels per day of oil and gas, making it the largest independent North Sea producer.

It aims to increase production to 200,000 bpd, Chairman Linda Cook has told Reuters