China's marine authority has found intermittent oil sheens?appearing near one of the two drilling platforms in Bohai Bay over the last week.

China's marine authority intermittent oil sheens were seen appearing near Platform C in the Penglai 19-3 oilfield, the largest offshore oilfield in China, over the last week.?[Xinhua]

The State Oceanic Administration said on its website that small slicks of oil are still emerging near Platform C in the Penglai 19-3 oilfield, and they urged U.S. oil firm ConocoPhillips to step up its efforts to clean up the oil spill there.

Small belts of oil, covering an area of 0.06 square kilometers on average, were also found near the platform every morning during the past week. They were all taken care of on the same day they appeared.

Between Sept 7 and Tuesday, an average of 3.6 liters of oil were seen each day, with new oil bubbling to the surface every minute. On Wednesday, it was down to 1.66 liters.

The monitoring results are expected to be updated on a daily basis from now on.

The oilfield operator ConocoPhillips China said in a statement on Thursday that the intermittent sheens occasionally rising to the surface at platform C are "a result of the residual oil droplets displaced during seabed clean-up activities around Platform C".

Divers have cleaned 5.84 cubic meters of oily mud from the seabed under Platform C in the eight days since Sept 7.

China National Offshore Oil Corporation, which holds 51 percent of the leaking Penglai 19-3 oilfield, said that it has approved plans submitted by ConocoPhillips China to depressurize the reservoir.

One plan proposes discharging fluids from various locations throughout the reservoir. Another outlines measures, which include drilling wells, designed to provide additional protection against any reservoir fluids polluting the seabed.

ConocoPhillips China said it has reported the plans to the State Oceanic Administration, which has yet to comment on them.

Since June 4, when the first oil spill was detected, the leaks at the two oil platforms in the Penglai 19-3 oilfield in Bohai Bay have polluted at least 5,500 sq km of sea.

ConocoPhillips said to China.org.cn that they sincerely regret the incidents in Bohai Bay and apologizes for the impact that the incidents have had on the Chinese people and the environment.

The company arranged for all the resources that they felt could be safely deployed for the clean-up, which included more than 900 personnel. In addition, they also have 60 to 70 divers and 6 dive ships supporting them in round-the-clock operations using vacuum technology to collect oil-based drilling mud from the sea floor.

As for a fund that ConocoPhillips China said it would establish to cover the cost of the clean up, the company said the details are still being discussed.