In what could be the world’s biggest IPO, Saudi Aramco has formally asked major banks to bid for potential roles in its planned initial public offering (IPO), according to a Reuters report.

According to sources, the requests for proposals were sent to banks few days ago, though there were no confirmations of which banks they were. Bankers attended the board’s meeting in Boston last month.

The planned IPO could raise $100bn and is the epicentre of the nation’s economic transformation process to bring in foreign investors and to implement diversification, moving away from oil.

An employee visits the site of crude oil storage tanks at the Juaymah tank farm at Saudi Aramco’s Ras Tanura oil refinery and oil terminal in Ras Tanura, Saudi Arabia, on Monday, Oct. 1, 2018. Photographer: Simon Dawson/Bloomberg

According to Saudi Arabia’s Crown Prince Mohammed bin Salman, Saudi Armco’s value is around $2 trillion and recently Saudi energy minister Khalid Al-Falih said Aramco would likely go public in 2020 or 2021.

In other news, Motiva Enterprises, the U.S. refining arm of Saudi Aramco signed an agreement to buy the Flint Hills Resources chemical plant adjacent to its Port Arthur, Texas, oil refinery, according to media sources. The deal will is expected to close by late 2019, will see Motiva operating the chemical plant while it constructs three petrochemical units within its Port Arthur Complex as part of an $18bn expansion along the U.S Gulf Coast, soruces added.

Recently, Saudi Armco signed a letter of intent to buy a 20% stake in India’s Reliance Industries’ oils-to-chemicals business, making it one of the largest foreign investments in India.

Meanwhile, oil prices gained roughly 2% yesterday after the Saudi oil field attack by Yemen’s Houthi forces. Brent crude LCOc1, the international benchmark for oil prices, settled at $59.74 a barrel, rising $1.10, or 1.88%.

U.S. West Texas Intermediate (WTI) crude futures CLc1 settled at $56.21 a barrel, up $1.34, or 2.44%, Reuters reports.