China oil stocks have had a rough week.

Shares of China's three state-owned oil and gas giants have suffered days of drops as U.S. oil prices recorded 12 consecutive days of declines.

Hong Kong-listed PetroChina, Sinopec and CNOOC opened down 2.9%, 2.3% and 4.4% respectively on Wednesday and fluctuated in the early morning as Brent Crude, the global benchmark, went down 6.6% at $65.47, entering a bear market.

The three oil stocks have declined for more than a week.