NEW DELHI: Saudi Arabian Oil Co (Aramco) buying a 20 per cent stake in Reliance Industries ' oil-to-chemical business will help it regain the position of being the biggest supplier of oil to the world's fastest-growing oil market.Saudi Arabia, which traditionally has been India's top oil source, lost the slot to Iraq during the last two financial years.This will change with Aramco buying 20 per cent stake in the RIL's oil-to-chemical (O2C) business, which has an enterprise valuation of $75 billion as it will be accompanied with a deal to supply 500,000 barrels per day or 25 million tonne a year of crude oil."Crude supplies of 500,000 b/d represents about 40 per cent of Reliance's crude intake, significantly higher than the stake taken, although Saudi Aramco historically supplied 20 per cent of Reliance's crude oil requirements," said Alan Gelder, vice president refining and chemicals at Wood Mackenzie.Saudi Arabia in 2018-19 fiscal exported 40.33 million tonne of crude oil to India, over 15 per cent short of 46.61 million tonne sold by Iraq, according to data sourced from the Directorate General of Commercial Intelligence and Statistics.Additional oil supplies following the Reliance deal will catapult Saudi Arabia to top spot again.The O2C business includes Reliance's refining and petrochemical divisions, and its 51 per cent stake in its fuel marketing business. The remainder 49 per cent stake in the fuel marketing business, which comprises of 1,400 petrol pumps and aviation fuel facilities at 31 airports, has been sold to BP for Rs 7,000 crore.The terms of the deal are yet to be finalised, but Reliance, going by the enterprise value announced by its chairman Mukesh Ambani on Monday, will get roughly $15 billion, including some debt adjustments, for the 20 per cent stake when the sale closes later this year.Gelder said the deal is further evidence that Saudi Aramco is executing on its long-term strategy to increase its refining and petrochemical capacity.Saudi Aramco continues to show a keen interest in accessing the Indian market, which has the strongest long-term growth prospects, he said.Following the same strategy, it along with UAE's ADNOC had signed up to take 50 per cent stake in a planned 60 million tonne a year refinery on the west coast. Aramco and ADNOC are to supply half of the crude oil required for the proposed refinery that will come up not before 2025.Saudi Arabia is keen to get a foothold in the world's fastest-growing fuel market to get a captive customer for the crude oil it produces. Crude oil is the basic raw material for the manufacturing of petrochemicals.Like other major producers, it is looking to lock in customers in the world's third-largest oil consumer through the investment. Kuwait is also looking to invest in projects in return for getting an assured offtake of their crude oil.Saudi Aramco is also keen on retailing fuel in India. A refinery in India can also be a base for it to export fuel to deficit countries in Europe and the Americas.India has a refining capacity of 247.6 million tonne, which exceeded the demand of 206.2 million tonne.Reliance's refining and petrochemicals assets include 1.2 million b/d of highly-sophisticated refining assets at Jamnagar in Gujarat. Both its refineries in Jamnagar are heavily integrated with petrochemicals.The company also has a world-leading position in polyester and intermediates, as well as steam crackers and polyolefins capacity at another four locations in India."This strategy is being achieved through a combination of project and acquisitions, with this acquisition following on from last year's acquisition of SABIC and SASREF, and the memorandum of understanding Aramco signed this year to acquire a 9 per cent stake in Zhejiang Petrochemical's 800,000 b/d integrated refinery and petrochemical complex in Zhoushan, China," he said.