Saudi Aramco’s repairs on its oil facilities that suffered devastating attacks last week are in emergency mode, but could still take several months before they’re fully operational again, according to the Wall Street Journal.

After the September 14 attack knocked out half of the country’s oil production, Saudi officials and oil contractors told the Journal that the estimate of 10 weeks that company executives have promised for a repairs timeline would be a fraction of the time it is now expected to take.

One Saudi official said costs could run in the hundreds of millions of dollars as the country and oil company are still reeling from the attacks. Saudi Aramco was readying for its IPO, which was slated to be the largest in history.

Read more: Photos show the scale of the destruction caused by the drone attacks on 2 Saudi Arabian oil facilities

The Journal noted that on Saturday, Aramco's Chief Executive Amin Nasser emphasized the company's stated repairs projection, saying that production would be back to normal levels by the end of the month and the facilities would return to maximum output capacity by the end of November.

"Not a single shipment to our international customers has been missed or canceled as a result of the attacks," he said, according to the Journal.

Satellite images published by the US government to the Associated Press shortly after the attack show an estimated 17 impact sites at the plants in Abqaiq, Saudi Arabia, and two at the nearby Khurais oil field.

The Journal notes that the locations of the strikes make it clear that the attacks were planned for maximum damage.

Officials reacted in horror to the attack, which affected 5% of the world's daily oil supply and wiped out more than 5 million barrels of oil each day.

Saudi Arabia accounts for 10% of the global oil output, according to UAE-based paper The National. Though Crown Prince Mohammed bin Salman announced plans to diversify the kingdom away from a dependence on oil in 2016, Saudi Aramco is still a major money-maker for the government.