An oil refinery in Germany on Thursday. Oil supplies are set to tighten further even if the U.S. and Iran reach a deal to end the war. | REUTERS

LONDON – Oil supplies are set to tighten further in coming weeks even if the U.S. and Iran agree on a peace deal to end their war because it will take weeks for oil shipments to resume from the Middle East Gulf and reach refiners worldwide — so oil companies will continue to deplete storage tanks to meet peak summer demand.

The world has used temporary buffers — commercial stockpiles, oil in transit or held in storage at sea and emergency reserves — to offset the shock from the war in the Middle East.…