New Delhi, March 16: ONGC Videsh (OVL) and a consortium led by Indian Oil today signed agreements to buy stakes in two Russian oilfields in Siberia for an estimated $4.2 billion.

IOC, Oil India and a unit of Bharat Petroleum (BPCL) signed a sale purchase agreement (SPA) for a 29.9 per cent stake in Taas-Yuriakh oilfield from Russia's Rosneft for $1.28 billion, top officials said.

The consortium also signed heads of agreement (HoA) with Rosneft for taking a 23.9 per cent stake in Vankor oilfield for a little over $2 billion.

Simultaneously, OVL, the overseas arm of state-owned Oil and Natural Gas Corporation (ONGC), which had in September last year bought 15 per cent in Vankor for $1.26 billion, signed an MoU envisaging its stake going up in the Siberian oilfield to 26 per cent by paying an additional $925 million.

The Taas-Yuriakh oilfield currently produces 20,000 barrels per day, officials said. The field has proven reserves of 137 million tonnes and output will reach 100,000 bpd in two years.

IOC, OIL and Bharat PetroResources Ltd (BPRL), a unit of BPCL, will after buying a 29.9 per cent stake in Taas-Yuriakh also pay $180 million as their share of future capex. They also signed an MoU with Rosneft for a possible stake in Vankor Cluster fields.

India, which imports 80 per cent of its energy needs, is seeking to enhance energy security amid low oil prices by tying up new sources of crude oil.

Rosneft, Russia's biggest oil producer, has been impeded by US and European economic sanctions over Moscow's involvement in the conflict in Ukraine. It needs to pay off debts incurred in its $55-billion acquisition of TNK-BP in 2013 and investments by India will help it to do so.

Rosneft and the Indian companies had signed preliminary agreements during Prime Minister Narendra Modi's visit to Russia.

Vankor is Rosneft's (and Russia's) second-largest field by production and accounts for 4 per cent of Russian output. It produces around 442,000 barrels of crude per day.

As of January 2015, it was estimated that the initial recoverable reserves were 476 million tonnes of oil and condensate and 173 billion cubic tones of gas.

The acreage of the field was 447 square km. Taas-Yuryakh had 167 million tonnes of oil and 181 billion cubic meters of gas.

The agreements were signed on the second day of Rosneft boss Igor Sechin's two-day visit to India.