Cheaper crude from Iran and Venezuela while international oil benchmarks were rallying was incentive enough for the world's top oil importer, China, to purchase in 2021 the most crude from the two U.S.-sanctioned exporters in three years, shrugging off risks of penalties from the United States.

Chinese refiners imported 53 percent more oil from Iran and Venezuela last year compared to 2020, according to estimates from market intelligence firm Kpler cited by Bloomberg. In total, China imported last year 324 million barrels of crude from Iran and Venezuela combined, the highest volume since 2018.

Private Chinese refiners, commonly known as teapots, purchased most of the crude from the two oil producers whose exports are otherwise being shunned by U.S. allies in Asia, such as Japan and South Korea. The risk of incurring secondary U.S. sanctions and potentially being cut off from the U.S. financial markets and system has not reduced the appetite for cheaper crude from Chinese independent refiners, according to the data cited by Bloomberg.

Imports of crude oil from Iran and Venezuela are not usually reflected in official Chinese customs data.

Officially, Iran's oil is under U.S. sanctions, and few buyers are willing to risk breaching those for fear of being sanctioned for dealing with Tehran themselves. Independent Chinese refiners, however, have never really stopped buying Iranian crude, although China's state giants are steering clear of trade with Iran's oil.

"This surge was triggered by rising crude prices, making Iranian crude, anecdotally, up to 10% cheaper when delivered into China," Anoop Singh, head of tanker research at Braemar ACM Shipbroking Pte Ltd, told Bloomberg.

Independent refiners in China boosted imports of oil from Iran between August and October, attracted by the cheaper Iranian crude despite the risk of running afoul of U.S. sanctions, Reuters reported two months ago, citing tanker-tracking data and traders. In November, independent Chinese refineries also increased their crude oil imports from Iran as the government issued a new batch of import quotas.