The first official glimpse of Saudi Aramco's financial performance confirms the state-run oil giant can generate profit like no other company on Earth: net income last year was $US111.1 billion ($156.1 billion), easily outstripping US behemoths including Apple and Exxon Mobil.

Crown Prince Mohammed bin Salman is trying to prepare Saudi Arabia for the "post-oil age." Credit:Bloomberg

But accounts published before the firm's debut in the international bond market also show Aramco -- an organisation that produces about 10 per cent of the world's crude -- doesn't generate as much cash per barrel as other leading oil companies like Royal Dutch Shell because of a heavy tax burden.

The bond sale, being pitched to investors this week in a global roadshow, has forced Aramco to reveal secrets held close since the company's nationalisation in the late 1970s, casting a light on the relationship between the kingdom and its most important asset. Both Fitch Ratings and Moody's Investors Service assigned Aramco the fifth-highest investment grade, the same as Saudi sovereign debt, but lower than oil majors Exxon, Shell and Chevron.

The company is preparing to raise debt in part to pay for the acquisition of a majority stake in domestic petrochemical group Sabic, worth about $US69 billion. The deal is a Plan B to generate money for Saudi Arabia's economic agenda after an IPO of Aramco was postponed. In effect, Crown Prince Mohammed bin Salman is using the firm's pristine balance sheet to finance his ambitions.