Iran can withstand a complete halt in oil exports of up to two months before being forced to curb production, analysts said, after the US began blocking shipping in and out of the country's ports on April 13.
The blockade could prevent roughly 2 million barrels per day (bpd) of Iranian crude from reaching its main buyer China.
Any Iranian production shutdowns would add to more than 12 million bpd of supply already disrupted by the regional war, tightening markets further and lifting oil prices.
With its exports blocked, Iran faces having to divert crude into onshore storage tanks. Once those tanks are filled, the OPEC member would be required to curb upstream output.
Consultancy FGE NextantECA estimates Iran has about 90 million barrels of available onshore crude storage capacity, out of total capacity of roughly 122 million barrels.
"Iran can sustain current production of around 3.5 million bpd for roughly two months without exports, extendable to around three months with a modest 500,000 bpd production cut," FGE NextantECA said in a note.
Iranian domestic refineries process about 2 million bpd of oil, they added.
The relevant Iranian authorities were not immediately available for comment.
Energy Aspects assumes significantly lower available onshore storage of about 30 million barrels, based on data from Kayrros.
Under that scenario, Iran could maintain current export levels for about 16 days before storage capacity runs out, based on export levels of 1.8 million bpd.
"The blockade may not have a significant impact on Iranian production in April, but if it continues into May then output would need to be reduced substantially," said Richard Bronze, co-founder of Energy Aspects.
He said the consultancy assumes Iran cannot utilize its full nameplate storage capacity, adding that historic data show stocks peaked at 92 million barrels in May 2020, which likely marks a realistic ceiling.
Bronze also said Iran will likely deploy available oil tankers in ports as floating storage, delaying production cuts.
The US military said more vessels were being turned back under the blockade, including the Chinese-owned tanker Rich Starry, which is under US sanctions and which was seen heading back through the Strait of Hormuz on Wednesday.
Eight Iran-linked oil tankers have been intercepted since the blockade began on Monday, the Wall Street Journal reported. A US destroyer stopped two tankers attempting to leave Iran's Chabahar port on the Gulf of Oman on Tuesday, a US official said.
