CNOOC announced it made two new exploration discoveries in the Bohai Bay off the Chinese coast.
The company said drilling operations at the Bozhong 8-4 and Kenli 10-4 wells encountered a combined 311 feet worth of oil reservoir and 36 feet of natural gas layer.
"The successful discovery of Bozhong 8-4 and Kenli 10-4 has extended our effective exploration activities in Bohai and further proven the rich oil and natural gas resources in this area," CNOOC exploration chief Zhu Weilin said in a statement Tuesday.
Bohai Bay is estimated to hold as much as 146 billion barrels of oil.
ConocoPhillips in 2011 observed "several small seeps" from a production platform in Bohai Bay associated with a release. Conoco said it had about 13,000 cubic feet of oil-based drilling mud cleaned up, which it said represented about 90 percent of the total volume released.