Companies including ExxonMobil and Valero Energy have shut down their facilities in the area and evacuated workers to safety.
Goldman Sachs estimates that the hurricane has taken three million barrels per day - or about 17% - of refining capacity offline, and that's likely to increase the overall level of crude oil inventories over the next couple of months.
"The slow moving nature of the storm will likely lead to these shut-downs continuing in coming days and may generate persistent damage as well," said Damien Courvalin, the head of energy research at Goldman, in a note on Monday. The note was emailed at 3 a.m. ET on Monday, and since then the storm has continued to crawl across Texas's southeastern coast.
Courvalin wrote that more refinery outages were to be expected, "with 850 kb/d of capacity in Houston not yet reported offline."
National Weather Service Harvey's path
The refinery outages are having a more immediate impact on gasoline futures, which jumped to two-year highs on Monday. It means drivers can soon expect higher prices at the pump.
Along the Gulf Coast, many areas will not have access to gasoline for days or even weeks, said Greg McBride, the chief financial analyst at Bankrate.com. "Those areas that do have gasoline will have long lines, high prices and frequently run out quickly," McBride said in a note.
Hurricane Harvey was the worst storm to hit Texas in half a century, with winds topping 130mph and as much as 50 inches of rain dumped around Houston. By Monday morning, it had subdued to a tropical storm with winds of up to 40mph.
While its impact is still being assessed, history shows that oil demand usually takes a number of months to recover after a big hurricane.
Goldman Sachs
The two outsized demand drops in the chart above were from Hurricanes Katrina and Rita in 2008, and Gustav and Ike in 2005.
"Two caveats to this historical template: the proximity of these pairs of hurricanes overstates the demand impact showed in Exhibit 10, while the magnitude of the onshore production impact of Harvey is unprecedented," Courvalin said.
In other words, there's still a lot that analysts don't know about the full impact of Harvey on refineries, just three days after it made landfall.
"I don't see it being an extended outage because of just the sheer need for [gasoline]," said Rob Thummel, portfolio manager at Tortoise Capital, which manages $15 billion in energy assets. "These companies are pretty resilient, they persevere through these catastrophes and have been through them before," he told Business Insider.
Here's Goldman's full list of the refineries at risk after Harvey:
Goldman Sachs