It was perhaps inevitable that pulling off the biggest I.P.O. in history would be a long and difficult task. But in the case of Aramco, the yearslong process has faced difficulties in the financial and geopolitical worlds, forcing Prince Mohammed to whittle his ambitions significantly.

The Saudi government has already had to postpone the offering several times, including last year, when it directed Aramco to buy control of a Saudi petrochemical producer, and earlier this month, when it decided to delay announcing the offering by several weeks to incorporate the oil company’s third-quarter financial report, according to the people with knowledge of the matter.

It is still possible that the government could change its mind and delay the offering again, these people added.

Even at $1.5 trillion, Saudi Aramco would be a colossus on global stock markets, with a capitalization far exceeding that of all its major petroleum rivals combined.

Formally known as the Saudi Arabian Oil Company, Aramco was founded in 1933 through an agreement between Saudi Arabia and Standard Oil, and it is widely regarded as a professional, well-run operation.

Its huge resources and scale — it earned $46.9 billion in the first half of the year and produced 10 million barrels a day — have given it unmatched financial and production advantages. That could give it a leg up on rivals like Exxon Mobil and Royal Dutch Shell with investors.

“There really is a limited pool of capital available for oil and gas equity investments, and there is a chance that Aramco is going to suck some of that up,” said Ben Cahill, research director at Energy Intelligence, a research firm.