China is on track to produce enough crude oil outside its borders to rival Opec members such as Kuwait and the United Arab Emirates, after its state-owned oil companies spent a record $35 billion buying foreign rivals last year.

In the first tally of the impact of China's recent overseas oil investments, the International Energy Agency calculates China's national oil companies will produce 3 million barrels a day abroad in 2015, double their 2011 overseas output of 1.5 million b/d and equivalent to Kuwait's annual output.

"China is set to become a major producing country outside of its borders," Fatih Birol, chief economist at the IEA, told the Financial Times on the sidelines of IP Week, an annual gathering of the oil industry in London. "A significant part of the increased foreign production comes from [merger and acquisition] transactions last year."

The surge of acquisition activity by Chinese oil companies - and their investment in unconventional drilling technologies - is reshaping the global oil industry.

Chinese national oil companies such as Cnooc and Sinopec have been on a buying binge over recent years, spending $92 billion since the start of 2009 on oil and gas assets in countries from the US to Angola, according to Dealogic. Last year, their acquisitions hit a record of $35 billion. Transactions involved joint ventures as well as outright purchases.