HOUSTON (NYTIMES) - The drone attack on one of Saudi Arabia's most important oil facilities could cripple a portion of Saudi petroleum exports for days or even weeks and send energy prices substantially higher.

But experts say that a severe shock to energy markets and the world economy is unlikely.

The attack on the Abqaiq processing facility and another plant, deep in Saudi territory, last Saturday (Sept 14) displayed the vulnerability of the kingdom to tensions in the Persian Gulf region.

The country produces about 10 per cent of the world's oil supplies. The disruption could slash Saudi Arabia's daily oil exports of 7.4 million barrels by as much as three-quarters, taking roughly 5 per cent of global supplies off the market, unless the facility is quickly repaired.

United States President Donald Trump suggested on Sunday that he could release supplies from the Strategic Petroleum Reserve, an attempt to calm oil markets.

In response, oil futures that had jumped more than US$11 a barrel when the futures market opened on Monday in Asia eased a bit to just more than US$7 a barrel higher.

The attack raised the possibility of further disruptions in Saudi Arabia's oil production if there are additional attacks on its fields and pipelines.

The planned initial public offering of the kingdom's national oil company, Saudi Aramco, could also be hurt if international investors doubt Saudi Arabia's ability to defend its vital energy infrastructure.

But as luck would have it, the attack came as global oil stockpiles were higher than usual, several producing countries have ample spare capacity and US oil facilities have so far been spared from a damaging hurricane season.

Meanwhile, a slowing global economy has moderated energy demand.

"We do not expect an immediate disruption on global oil trade, since many nations, including the US, have ample crude oil in storage," said Mr Manish Raj, chief financial officer of Velandera Energy Partners, a Louisiana oil exploration and production company.

"The Saudis themselves have enough storage to meet their export obligation for the next 60 days. Therefore, we expect no supply-demand imbalance in the near term."

The main uncertainty is how long will it take for the Saudis to repair the Abqaiq facility, which separates gas from oil from several important oil fields.

While the fires set off by the attack were put out quickly, the Saudis may not know the answer for days since the facility is large and has complex equipment that still needs to be tested.

Should the damage be fixed quickly, Eurasia Group, a risk consulting firm, estimates that oil prices could rise a modest US$2 to US$3 a barrel, which would still leave the global benchmark Brent crude below US$65 a barrel, relatively low by recent historical standards.

The firm estimated that a more long-lasting disruption could mean an increase of US$10 a barrel, though that would still leave prices several dollars below where they were a year ago.

Other analysts took a dimmer view, even as Saudi Aramco said on Sunday that repairs were already underway. The initial reaction of oil traders was panicky.

"The problem is that the attack is so significant," said Mr Bill Farren-Price a director at RS Energy Group, a market research firm.

"It demonstrates that one of the best regional oil companies has difficulties defending itself from this new style of threat. That theme is going to endure."

There are doubts the Saudis will be able to maintain their usual exports and satisfy domestic consumption.

"Export volumes will be severely impacted," Mr Clay Seigle, an analyst at Genscape, a market research firm, said in an e-mail.

"The market will be left with a thinner cushion against additional supply disruptions, and traders will bid prices higher as a result."

How the other countries in the Saudi-led Opec will respond is not yet clear. In a phone conversation, an official with the Organisation of the Petroleum Exporting Countries said that the Saudis had so far not shared information about the extent of the damage and when output might be restored. He also said that Opec had not yet begun discussions on potentially loosening supplies.

"We have to see how the market reacts tomorrow," the official said.

The average price for a gallon of regular gasoline in the United States was US$2.57 on Sunday, 28 cents lower than it was a year ago. That decline has been a boon to consumers, giving them extra spending power that has helped retailers and restaurants.

An increase in prices to last year's levels is possible over the next few weeks unless the Saudi facility is quickly fixed, energy analysts said.

Only a decade ago, the attack would probably have sent oil prices soaring. But that was before US oil production climbed with the shale drilling frenzy.

The US now produces roughly 12.1 million barrels a day, double what it produced in 2012 and 1.4 million barrels more than only a year ago.

It imports about 630,000 barrels of Saudi oil a day, down about half from 2017.

The US and other developed countries have nearly three billion barrels in stockpiles, according to the International Energy Agency, enough to take care of about two months of demand. That is about 50 million barrels above a year ago, despite US sanctions on Iran and Venezuela that have constricted their exports.

The stockpiles of the industrialised countries are at their highest level since September 2017, and are nearly 20 million barrels above the average of the last five years, according to the energy agency.

"For now, markets are well-supplied with ample commercial stocks," the agency said in a statement last Saturday, adding that it was "monitoring" the Saudi situation.

Saudi Arabia has roughly 27 days of supply stockpiled, according to S&P Global Platts, a provider of energy information. That stockpile is stored not only in the kingdom but also in Egypt, Japan and the Netherlands for added security.