A major U.S. pipeline is still mostly shut due to a cyberattack. Here’s what you need to know

The United States’ largest fuel pipeline has been mostly shut since Friday after a cybersecurity attack — and it’s not clear how long the outage will last.

Wells Fargo says the restart date is key, and outlined three possible scenarios for reopening that could help investors gauge the possible impact.

The operator of Colonial Pipeline fell prey to a ransomware attack on Friday, forcing all pipeline operations to stop. Colonial Pipeline said Sunday it is developing a system restart plan, and that some smaller lines are now operational.

The company said it will “bring our full system back online only when we believe it is safe to do so, and in full compliance with the approval of all federal regulations.”

3 possible scenarios
“Timing of the restart is the critical issue,” said analyst Roger Read in a note on Sunday. He outlined three possible date ranges:

1. Fewer than five days: If a partial restart of the pipeline begins by Wednesday, there will be “no significant or lasting impacts.”
2. Six to 10 days: Refiners may need to reduce the amount of crude oil they process if the pipeline remains shut for up to 10 days. Inventories will rise in the U.S. Gulf Coast, causing prices to fall, while prices in the East Coast would jump, the analyst said. The East Coast is also likely to import more waterborne fuel, and spot shortages will start to take place in parts of the Southeast of the U.S.
3. More than 10 days: Refiners in the Gulf Coast will almost definitely have to reduce their runs, and oil prices may weaken compared to waterborne crudes to encourage exports. “Expect significant fuel shortages in the interior Southeast of the U.S.,” Wells Fargo said in the note.

Why it matters
Colonial operates the country’s largest refined products pipeline and transports 2.5 million barrels per day, according to its website. It connects refineries from the U.S. Gulf Coast to more than 50 million people in southern and eastern U.S.

The pipeline transports gas, diesel, home heating oil and jet fuel.

Which scenario is likely?
Patrick De Haan, head of petroleum analysis at GasBuddy, said there hasn’t been much information on when the pipeline could come back online.

“Even well-placed sources I’ve talked to really have nothing to say, and so the market really has no idea if this could be online tomorrow, if it’s going to be three days,” he said.

That may be why the market has responded “very cautiously