HOUSTON (Bloomberg) --Oil prices have surged more than 75% in the U.S. this month. But don’t expect a quick rebound in supply from shale explorers.

The quick turnaround in oil markets is exposing the shale industry’s Achilles’ heel: Lightning-fast production declines. Shale gushers turn to trickles so quickly that explorers must constantly drill new locations to sustain output.

And they haven’t been doing that. Drilling activity touched an all-time U.S. low after Covid-19 lockdowns crushed global energy demand and explorers slashed spending to survive a crash that has erased tens of thousands of jobs and pushed some companies into bankruptcy.

It’s a phenomenon that’s ultimately attributable to the very geology of shale. Just like a shaken bottle of champagne explodes when its cork is popped, a fracked shale-oil well erupts with an initial burst of supply. The froth is short-lived, however, unlike old-fashioned wells in conventional rocks that are characterized by steadier long-term production rates. To offset the decline curve, shale explorers used to keep drilling. And drilling. And drilling.

“We just have no new drilling and these decline curves are going to catch up,” said Mark Rossano, founder and chief executive officer of private-equity firm C6 Capital Holdings LLC. “That hits really fast when you’re not looking at new production.”

Shale explorers have been turning off rigs at a record pace because the oil rout has gutted cash flow needed to lease the machines and pay wages to crews. Going forward, management teams may be hesitant to rev the rigs back up again despite higher crude prices because of fears of flooding markets with oil once again and triggering yet another crash.

Left unchecked by new drilling, oil production from U.S. shale fields probably would plummet by more than one-third this year to less than 5 million barrels a day, according to data firm ShaleProfile Analytics. That would drastically undercut U.S. influence in world energy markets and deal a major blow to President Donald Trump’s ability to wield crude as a geopolitical weapon.

Such is America’s reliance on new drilling that 55% of the country’s shale production is from wells drilled in the past 14 months, according to ShaleProfile.

“These are much bigger wells than your small onshore conventional wells. We’re in a whole other ball park here,” said Tom Loughrey, founder of shale-data firm Friezo Loughrey Oil Well Partners LLC. “We have these relatively large and numerous shale wells, but they decline fast.”

To get an idea of how dramatically shale wells peter out, consider this: less than 20% of this year’s expected drop in overall U.S. crude output will come from shuttering existing wells, according to IHS Markit Ltd. Rather, the vast majority of the supply drop will be the direct result of canceled drilling projects.

Cliff Edge. “If you want to be a highflier and a fast grower, you do that by adding lots of new wells,” said Raoul LeBlanc, an IHS analyst. But when the drilling stops, slumping output produces “a hangover effect.”

Some explorers are taking more drastic action than others. While Parsley Energy Inc. and Centennial Resource Development Inc. have said they’re halting all drilling and fracking, companies such as EOG Resources Inc. and Diamondback Energy Inc. plan to continue adding new wells, albeit at a severely reduced pace.

Much of the shuttered production probably will be turned back on by the end of this year, Federal Reserve Bank of Dallas President Robert Kaplan said during a Bloomberg Television interview.

Companies often don’t disclose their decline rates until asked, and even then, not everyone is happy about it. Shale pioneer Mark Papa, who founded EOG and until recently led Centennial, once reprimanded an inquisitive analyst.

“Subash, we don’t disclose decline rates,” he said during a February 2019 conference call in response to a question from then-Guggenheim Securities analyst Subash Chandra. “That’s kind of one of those things – kind of an entrapment question, so that’s just something that we really don’t want to talk about.”

Asked about his company’s decline rates earlier this month, Cimarex Energy Co. CEO Tom Jorden responded, “I hate it.”