Iraq has already begun shutting in production as exports through the Strait of Hormuz become increasingly constrained. Roughly 1.5 million barrels per day are reportedly offline, and officials have warned that figure could approach 3 million bpd if disruptions persist.
At 3 million bpd, this becomes one of the largest sudden supply losses in the modern market outside of sanctions or war.
Iraq’s total crude production has been running near 4.0–4.3 million bpd, according to recent OPEC secondary-source data. Exports typically average between 3.2 and 3.4 million bpd, the vast majority shipped from southern terminals at Basrah. China and India together account for roughly two-thirds of those flows, making Iraq one of Asia’s most critical heavy crude suppliers.
That output is heavily concentrated in the southern fields feeding Basrah exports. Rumaila alone has nameplate capacity of around 1.4–1.5 million bpd and routinely produces well above 1.3 million bpd. West Qurna 1 produces roughly 600,000 bpd, with capacity closer to 650,000–670,000. West Qurna 2 is producing around 460,000 bpd, though development plans have targeted 750,000–800,000. Zubair’s design capacity is roughly 700,000 bpd. The Maysan complex contributes roughly 300,000–350,000 bpd.
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Taken together, those fields account for the bulk of Iraq’s export engine. A 3 million bpd shut-in would effectively sideline most of the southern system and remove a significant share of medium and heavy sour barrels from global trade.
The obvious question is whether OPEC can replace those barrels.
And the answer depends on who you ask and how you define spare capacity. But even theoretically, it’s a stretch. In December last year, the EIA redefined the terms “maximum sustainable capacity” as the upper limit a producer could reach within a year if everything runs smoothly and “effective capacity” which is the amount of oil that could be realistically brought online within 90 days and sustained without damaging fields or infrastructure.
Let the terms “90 days” and “with a year” sink in for a moment.
For the sake of exactness, the EIA defines spare capacity using the second of those terms.
So, does OPEC really have the spare capacity to meaningful fill the gap right now?
Under that 90-day definition, OPEC’s effective spare capacity is generally estimated in the range of roughly 3 to 4 million barrels per day. And almost all of it sits in just two countries: Saudi Arabia and the United Arab Emirates. Saudi Arabia accounts for roughly 2 million barrels per day of that cushion. The UAE contributes somewhere around 0.8 to 1.0 million barrels per day. The rest of OPEC’s members add relatively marginal volumes.
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If Iraqi shut-ins approach 3 million barrels per day, you are no longer talking about dipping into spare capacity. You are talking about testing the outer boundary of it and would be almost entirely reliant on two producers ramping quickly, sustaining output, and pushing those barrels through the very same Strait of Hormuz that is currently under strain. And those spare capacity figures include everything that could take them 90 days to turn on.
OPEC could potentially turn on all its spare capacity, but it could take them months to do it. Mobilization is not instantaneous.
Just as importantly, crude oil quality matters. Iraqi exports are mostly comprised of medium and heavy sour grades. Refiners in China and India, which together take roughly two-thirds of Iraq’s exports, take about 2.1-2.5 million bpd—and they are largely configured for those heavier grades. Substituting lighter grades alters yields, diesel output, and refining margins. This is already playing out in today’s tightening heavy crude differentials.
And finally, even with the upstream issue resolved, the oil would still have to move.
Even if Saudi Arabia and the UAE open the taps, much of those exports would still need to transit the Strait. If traffic slows, if insurance costs spike, if tankers hesitate, the constraint shifts from upstream capacity to physical flow. Spare capacity in a field does not equal barrels on a ship.
And timing matters. The EIA’s definition allows up to 90 days to bring that oil online and sustain it. Ninety days is a long time in a market reacting in real time. A 3 million bpd disruption doesn’t give producers a comfortable ramp window. It forces a response under pressure.
So yes, OPEC has spare capacity on paper. But if Iraqi shut-ins approach 3 million bpd and linger, the discussion would quickly stop being about headline spare capacity and would instead be about deliverable barrels — in the right quality, moving through functioning shipping lanes. That is a much narrower margin of safety than the top-line numbers imply.
By Julianne Geiger for Oilprice.com
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