Reliance Industries will sell 20 per cent stake in its oil and chemicals business to Saudi oil giant Aramco for about $ 15 billion and nearly half of its fuel retail business to BP of UK for Rs 7,000 crore. Aramco, the world's biggest crude exporter, will also supply Reliance's twin-refineries at Jamnagar in Gujarat with 7,00,000 barrels of oil a day on a long-term basis, Ambani said.