The storage clock is ticking as tankers that exported 3.2 million barrels of crude oil per day remain bottled up in Iranian ports due to the blockade by the U.S. Navy.

The blockade is part of a global vise denying Tehran $13 billion in monthly revenues and seeking to paralyze Iran’s petroleum industry by forcing it to shut down when it runs out of space to store what it can’t ship.

Since U.S. President Donald Trump imposed the blockade on April 13, at least 1.5 million barrels of Iranian oil have been stored every day because there’s no place to move it.

Those barrels are starting to pile up. According to consensus industry estimates, including by UK-based Energy Aspects, up to 68 million barrels of Iran’s 122 million barrel maximum storage was full in late April, with space for 20 million to 30 million barrels more.

The squeeze is rattling Islamic Republic leaders, Trump said in an April 28 Truth Social post.

“Iran has just informed us that they are in a ‘State of Collapse.’ They want us to ‘Open the Hormuz Strait,’ as soon as possible, as they try to figure out their leadership situation,” the president wrote.

The president has expressed confidence that Iran will soon meet his demands to terminate nuclear weapons development, end support for terrorist groups, and withdraw its territorial claim—and control—of the strait.

To calculate when these “state of collapse” concessions will manifest, time and space become coefficients in a pencil-and-napkin math equation. The answer is a so-called storage clock. It has one fulcrum constant: More time equals less space.

Kpler and JP Morgan analysts were among those in late April doing storage clock math, projecting that Iran would run out of time and space within 15 to 22 days—mid- to late May—if it can’t ship oil.

“Iran is being pushed into a storage-driven shut-in cycle,” analyst Homayoun Falakshahi wrote in a separate April 29 Kpler analysis. “Iran faces imminent forced shut-ins, with storage saturation likely within ~20–24 days, triggering rapid production cuts.”

Energy Aspects projected in late April that it could take up to seven weeks, or until mid-June, for the blockade to force shut-ins and shutdowns. Analyses by Wood Mackenzie, Atlantic Council, the Center for Strategic International Studies, and the Center on Global Energy Policy at Columbia University, among many others, offer timelines that fall between.

Some maintain Iran’s storage clock has already expired. The Institute for the Study of War and The Critical Threats Project at the American Enterprise Institute said Iran’s storage was depleted as of April 29.

The Foundation for Defense of Democracies projected there would be a shutdown by April 25.

“Extremely important topic is the storage clock,” foundation senior fellow Miad Maleki, a former U.S. Treasury executive, wrote in an X post. He estimated Iran had approximately 20 million barrels of storage left on April 12 and predicted that within 13 days of maxing out capacity, “Iran must shut-in wells.”

No Way Out

Iran has four oil- and gas-producing regions. The Khuzestan fields have been producing since the 1960s, generating about 2.2 million barrels per day. West Karoun on the Iraqi border produces 500,000 barrels per day. The provinces of Fars and Bushehr along the Gulf mostly produce offshore natural gas, including from South Pars, the Iranian sector of Qatar’s North Field, the world’s largest gas field. The fourth region is Iran’s Persian Gulf fields, with about 65 percent originating from the Kharg district’s three fields.

All roads, railways, and pipelines, and virtually all hydrocarbons extracted from Iran’s oil and gas fields, lead to Kharg Island, an eight-square-mile coral outcrop 300 miles north of the Strait of Hormuz that houses more than 25 percent of Iran’s storage capacity.  Ninety percent of Tehran’s oil exports is pumped from terminals at Kharg into supertankers, up to 10 at a time.

By April 20, one week after the United States implemented the blockade, stored oil at Kharg Island was at 74 percent capacity, Center on Global Energy Policy fellow Antoine Halff wrote in an April 28 analysis.

U.S. Treasury Secretary Scott Bessent wrote on X on April 21 that storage on the island would be full “in a matter of days“ and that ”the fragile Iranian oil wells” would be shut in.

Four of Iran’s five other export-capable ports—Sirri and Lavan islands, Saroosh, and Assaluyeh near Bushehr—are inside the Gulf. Only Jask is south of the strait, although no ships are using its newly built terminal on the Gulf of Oman with the U.S. Navy lurking nearby.

While Iran has a robust domestic pipeline network, it only receives crude via cross-border pipelines for refining from Kazakhstan and Turkmenistan, and only exports natural gas in pipelines to Turkey, Iraq, and Armenia.

Tehran has limited capacity to expand exports by rail, although Iran Oil Exporters Union spokesman Hamid Hosseini said in widely reported comments that the regime is considering shipping oil by train on a newly built rail corridor from Iran to Yiwu and Xi’an in China.

Unless the U.S. Navy lifts its blockade, Iran cannot move oil and gas out of the country, putting the same squeeze on Tehran that it has imposed on its Gulf State neighbors since early March—menacing the Strait of Hormuz, bringing Gulf trade to a standstill, damaging ports and infrastructure in drone and missile strikes, and marooning an estimated 20,000 sailors on ships anchored in limbo on “the Arab side” of the Gulf.

“When Iran first disrupted tanker traffic in the Strait of Hormuz, those Arab producers with the least available storage capacity and no export alternative were quick to ramp down production,” Halff said. “With the United States now restricting marine traffic to and from Iranian ports, Tehran faces the same conundrum.”

Shutdown Stresses

When the storage clock expires, wells are capped—or shut in—rigs disassembled, field grids unplugged, refineries shut down, and men and machines idled. Restoring production to pre-shutdown capacity can take weeks or even months.

The longer that oil and gas infrastructure is offline and marginally manned, the more vulnerable it is to structural damage and, as Trump noted, the more prone it is to “explode” from unvented pressure.

“Long-term shut-ins could lead to corrosion of wells and pipelines, the settling of sand and debris in the wellbore or pumps, or the mechanical deformation of the wells,” Robin Mills, a fellow at the Center on Global Energy Policy, wrote on the center’s website. “Careful technical planning of shutdowns and restarts … can fix most of these problems.”

The potential for long-term damage to Iran’s energy infrastructure during a shutdown is compounded by its “wax” oil, a heavy crude that can solidify and block wells and pipelines when not flowing.

“There is some anticipation that the need to shut-in producing wells and fields will cause damage to facilities, cause them to ‘explode,’ or permanently reduce Iran’s oil production capacity even if and when the blockade is eased,” Mills wrote.

Another potential threat to shut-in wells is water coning.

“When mature oil wells shut down, bottom water rushes in, a process called water coning,” Maleki wrote on X.

“Oil droplets get permanently trapped in rock pores. This oil can never be recovered.

“Forced shut-ins could permanently destroy 300,000-500,000 bbl/day of production capacity, that’s [$9 billion to $15 billion per year] in revenue, gone forever.”

The risk of “impairment from prolonged shut-ins … is real, but highly field-specific,” Siamak Namazi, an Iranian business executive imprisoned for eight years by the regime before his 2023 release, wrote in an April 29 Middle East Institute analysis.

Iran’s biggest fear in recovering from a shutdown is not that it “would suddenly lose the ability to pump oil,” he said, “but that some fields could return more slowly, at lower rates, or with lasting reductions in productive capacity.

“In other words, the damage would likely be partial, uneven, and costly—not absolute.”

Wily, Resilient Foe

Several analysts, including Kpler’s Falakshahi, cautioned that even in a “state of collapse,” the Islamic Republic is unlikely to cede to U.S. demands without concessions. Tehran’s National Iranian Oil Co. “has strong expertise” in surviving a half century of sanctions, as well as the Iran–Iraq war and 2020’s COVID-19 shipping shutdown, among other adversities, he said.

“The reality, however, is that Iran has shut in oil production in the past without serious repercussions (as have other oil producers), although gas production may have to be cut back,” Mills wrote.

Rotating shut-ins across wells, rather than fully idling fields, is among the ways Iran has avoided full lockdowns in the past. According to widespread media reports, Iranians are stashing oil in old tankers and in “junk storage”—in anything, anywhere possible.

Halff notes there is likely underestimated onshore storage embedded in “structurally long storage capacity relative to exports”—meaning long distances from well to port—in central and southern Iran.

Iran has made significant investments “to increase alternate storage and export facilities over the past 10 years,” he said, which “suggest the country may not be in imminent danger of a major crude oil shut-in.”

“The pressure on Tehran is real,” Namazi said, cautioning that Iran operates under its own rules. “Production losses that look decisive on a spreadsheet may carry less weight in the regime’s calculus than many Western analysts assume.”

Since 1979, the Islamic Republic “has prioritized survival, coercive leverage, ideological commitments, and internal control over economic welfare,” he said. “It has tolerated sanctions, isolation, inflation, capital flight, and deep economic damage when leaders judged those costs preferable to strategic concession.”

Namazi dismissed “countdown narratives” as “dangerous,” warning not to “make a deeper analytical mistake in assuming the Islamic Republic weighs costs the way a normal commercially minded state would. It does not. The prospect of losing oil production capacity is highly unlikely to convince current decision-makers in Tehran to concede to American demands.”

The standoff in the strait has raised energy costs in the United States, with the national average for gas topping $4 a gallon and November’s midterms—with slim Republican majorities imperiled—drawing nearer. Many analysts think Iran believes it can outlast an impatient Trump.

“Tehran may also be betting that its tolerance for pain exceeds that of its rivals and an oil-sensitive global economy—that others will seek relief long before it seeks compromise,” Namazi said.

‘Arab Side of the Gulf’

Reuters reported that Goldman Sachs estimated Gulf crude production on April 24 was running 57 percent below pre-war 20 million bpd levels, with roughly 14.5 million bpd capacity offline in Saudi Arabia, United Arab Emirates, Kuwait, Qatar, and Bahrain.

The U.S. Energy Information Agency projects if the impasse extends beyond mid-May, Gulf exports could dip below 9 million bpd, with half exported via Saudi Arabia’s East-West Pipeline to Yanbu on the Red Sea.

Iranian control of the strait has not only stymied Gulf export economies, but Tehran’s missile and drone attacks on “the Arab side of the Gulf” have disabled production, causing billions in damage that will require months to restore to pre-war production.

A March 18 missile strike destroyed Qatar’s Ras Laffan Industrial City Pearl plant that liquifies natural gas for transport. QatarEnergy CEO Saad al-Kaabi said it will take up to five years to rebuild.

Since the war began, the UAE has intercepted 314 ballistic missiles, 1,672 drones, and 15 cruise missiles launched by Iran, according to the Emirati defense ministry.

The pressure from Iran’s control of the strait is exposing fissures, with some Gulf states supporting the United States’ campaign and others allegedly amenable to negotiating a separate peace with Tehran. That friction came to fracture when the Emirates announced April 28 it would exit OPEC, effective May 1, to pursue “sovereign responsibility in a new energy age.”

“It’s a bombshell announcement. I’m still shocked thinking about it,” said Amena Bakr, Kpler’s head of Middle East energy and OPEC+ insights, during an April 30 webinar. She noted that tensions between the Emirates and Saudi Arabia had “been bubbling under the surface for a while.”

“We’ve heard Emirati officials come out publicly and say they feel some Arab states didn’t do enough for them when they were attacked by Iran,” she said. “As you know, Iran was targeted on the [Emirates] even more than Israel.”

William Reinsch, Scholl chair emeritus at the Center for Strategic and International Studies in Washington, wrote in an April 22 analysis that the war has “exposed the fragility of the smaller countries in the Persian Gulf.”

Gulf States “spent decades trying to convince the world they are safe and reliable destinations for foreign investment, manufacturing, tourism, and transit,” he said. “The war has shattered that illusion. While infrastructure can, and will, be repaired, investor and visitor comfort levels will be much harder to restore. People and money will start to look elsewhere.”