The expansion blueprints of Chinese oil companies overseas are currently facing "unprecedented challenges", which means that the State-owned enterprise giants should prepare for the unexpected, according to a former executive of China National Petroleum Corp.

Both geopolitical and economic risks have surged recently, a situation China has not encountered in recent decades, and have slowed the oil companies' pace of expansion overseas, said Chen Geng, a deputy of the National People's Congress (NPC) and the former general manager of CNPC.

"It is now a good time to launch mergers and acquisitions overseas, because the rising oil price is lifting the market value of public companies, adding to costs and potential risks," said Chen.