As Iran’s oil storage fills to capacity under the American naval blockade of the Strait of Hormuz, a term from petroleum engineering has suddenly acquired geopolitical weight: water coning.

Water coning describes what happens when an oil well is pumped too aggressively, or — critically — when it is shut in and then restarted. The boundary between oil and the denser water beneath it warps upward, forming a cone that invades the wellbore. The well chokes on water. Production collapses. If the operator is unlucky, the reservoir is permanently damaged.

Iran now faces exactly this lose-lose. Kpler and JPMorgan analysts estimated in late April that Tehran had between 12 and 22 days of unused storage capacity remaining. Storage at Kharg Island — through which the bulk of Iran’s exports normally pass — was at 74 per cent capacity by April 20. When tanks fill, wells must be shut in. And Iran’s ageing Khuzestan fields, many producing since the 1960s, are precisely the kind of mature, high-water-cut reservoirs most vulnerable to water intrusion during prolonged shutdowns. The Columbia Center on Global Energy Policy judged that Iran’s oil sector can likely weather shut-ins overall, but acknowledged that water coning remains a particular risk in marginal wells with high water-cuts, low reservoir pressure, or ageing infrastructure — a description that fits a non-trivial share of Khuzestan’s legacy operations.

Tehran insists it has the expertise to manage orderly shutdowns, honed through decades of sanctions. Perhaps. But the physics is unforgiving: when production halts, formation water migrates into oil-bearing zones, and when it does, the damage can become entrenched. Wells that restart after prolonged shut-ins often produce far more water and far less oil — permanently. Iran’s dilemma is not political theatre.........

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