Chinese energy and petrochemicals giant Sinopec plans to take a stake in Russian petrochemical giant Sibur, it has been revealed. The stock handover is planned to be completed by Dec. 1 2015 after the necessary regulatory approvals.

While the two companies have declined to disclose the size or the value of the proposed stakeholding, Russian sources told the news agency Reuters that Sinopec could acquire more than 10%. The deal signed in Beijing during Russian President Vladimir Putin's visit would not substantially alter the Chinese company’s shareholder structure, however.

Businessman Leonid Mikhelson, head of Novatek, Russia's second largest gas producer behind Gazprom, is expected to remain Sibur's largest shareholder. Other Sibur shareholders are tycoon Gennady Timchenko, regarded as an ally of Russian President Vladimir Putin, as well as current and former Sibur managers.

In a statement, Sinopec chairman Wang Yupu said Sibur’s vertically-integrated upstream and petrochemicals business model is highly complementary with Sinopec’s structure, and the transaction is in line with the Chinese company’s objective to strategically expand overseas. In particular, a partnership with the Russian company would diversify and assure sourcing of petrochemical products.

Sibur chairman Leonid Mikhelson said the deal would “reinforce Sibur’s expertise to maximize the efficiency of new large-scale projects and raise the company to a new level.” Earlier this year, the Russian and Chinese companies signed strategic cooperation agreements in trading operations as well as examining opportunities for cooperation on gas processing and petrochemicals.

For 2014, Sibur reported sales revenue of 361 billion Russian rubles ($5.4 billion).