Three crew members remain missing, CNOOC Ltd said on Friday, after a well blowout and fire on a platform in Bohai Bay earlier this week that has partially halted operations at China's largest offshore oilfield.

The impact of the incident at the wellhead platform in the Penglai 19-3 field on CNOOC Ltd's annual production is up to approximately 600,000 barrels of oil, representing 0.1% of the total target of 545 million to 555 million barrels of oil equivalent.

State-controlled CNOOC Ltd operates the field on 51% and is joined by US independent ConocoPhillips on 49%.

With the incident set to hit CNOOC Ltd's equity production this year by 600,000 barrels, this represents some 1.2 million barrels, inclusive of ConocoPhillips' share.

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The blaze hit wellhead platform V on the Penglai 19-3 field on 5 April after a blowout in the well V29, CNOOC Ltd said in a statement on Friday, confirming an earlier Upstream report.

“Kicks and fire occurred on the V platform” of the Pengbo Operating Company of CNOOC Ltd, but was extinguished on Tuesday with no spill or environmental pollution having been reported, the statement read.

Upstream previously reported, citing sources familiar with the incident, that the fire was still burning on Thursday.

Fire broke out in the evening of 5 April when shallow gas overflowed during drilling operations in well V29 of the V platform, CNOOC Ltd said, adding that the company immediately initiated emergency response procedures and carried out well kill operations.

When the incident occurred, there was a total of 102 people on the platform, 99 of whom were evacuated that night while the other three were reported missing.

In response to the accident, CNOOC has dispatched vessels, helicopters and drones in a search and rescue mission for the three missing personnel. It also carried out an oil spill check and placed oil booms around the platform.

The Penglai 19-3 oilfield lies in Bohai Bay Block 11/05 in water depths ranging from 27 to 33 metres. The block also contains the Penglai 19-9 and 25-6 oilfields.

CNOOC holds a 51% operating interest in the fields, with ConocoPhillips holding the remaining 49% equity.

The field started production in 2003, but was forced to shut down in September 2011 following an oil spill.

ConocoPhillips, which was then operator, paid 1.68 million yuan ($256,234 today) to 21 farmers who said their livelihoods were hurt by the spills and did not participate in a previous 2012 settlement with ConocoPhillips and CNOOC Ltd.

The 723 barrels of leaked oil 2620 barrels of oil base mud spread across 5500 square kilometres of water in Bohai Bay. The spills were sealed in October 2011, and the field, with daily production of about 160,000 barrels, was restarted in February 2013.

The field is now producing about 80,000 bpd versus its peak of 168,000 bpd from seven platforms before 2011.

CNOOC Ltd last year produced 165.7 million barrels per day from Bohai Bay.

The company expects to produce a combined 15,681 barrels of oil from Penglai 19-3 and Penglai 19-9 next year.

The field is serviced by the Hai Yang Shi You 117 floating production, storage and offloading vessel.