ConocoPhillips, part owner of China\'s biggest offshore oilfield, started reopening wells to ease reservoir pressure after leaks caused the country\'s worst spill in more than a year. The US oil producer, which owns 49 per cent of the Penglai 19-3 field in Bohai Bay, has started discharging fluids at Platform B, the company\'s China unit said in a statement on its website yesterday. Leaks at platforms B and C, two of five at Penglai 19-3, have polluted 870 square kilometres of Bohai Bay since June. The spills prompted China\'s government to shut the entire field on September 2 and Penglai\'s co-owner CNOOC Ltd. to lower its full-year output estimate by as much as 9.3 per cent.