Wang Zhen, a professor with the China University of Petroleum, said CNOOC has a simpler business structure compared with the other two giants－CNPC and Sinopec. Unlike the other two, who have refining business and natural gas presence, CNOOC has limited downstream business to offset the pressure from lower crude prices.

CNOOC posted a 4.6 percent decline in third-quarter sales as lower crude prices eroded earnings.

The International Energy Agency, however, offered a ray of hope amid negative sentiment for the oil sector last week. The agency scaled down its 2015 non-OPEC oil supply forecast and said crude prices could see a recovery in the second half of the year.

But some analysts are still cautious on Asian energy stocks. HSBC in late January downgraded China's oil giants on the assumption that an oil recovery will be long and slow. JP Morgan followed suit and said oil has not bottomed out and most of the government policies are against the oil majors. Some institutions believe that even if the oil prices stabilize, or even recover, the refining margins of Chinese refiners will still be under pressure.

For one thing, the Chinese government is raising taxes on refining products, which is directly squeezing companies' profit. Meanwhile, there is also the regional supply issue. While there is now less production in North America, more supplies are being built in Asia, which put added pressures on the existing players, UBS analyst John Chung said in a research note last month.