The Chinese player reported a net profit of 5.2 billion yuan ($818 million) in the three-month period, a significant drop from 28 billion yuan in the comparable period of last year.
Revenues also fell by 28% to 427 billion yuan, compared to 600 billion yuan in the third quarter of 2014, the state-controlled company said on Thursday.
According to the company, oil output since January was up 3.3%