Operationally, pulling oil out of tanks when levels fall below the so-called “suction line” is difficult and expensive, and the quality of crude can be compromised by the presence of water and sediment. 

For now, traders are expecting stockpiles to halt their decline by October and possibly start building up again, depending on how exports shape up. Indeed, this week’s drawdown was less than 1 million barrels — the first time that’s happened since early August.

Cushing’s role in global oil markets has also diminished in recent years since the US lifted an export ban. Most barrels now flow straight from the prolific oilfields in Texas’ Permian Basin to the coast, where they are shipped to overseas buyers.

Eoin Treacy's view

Shale oil producers are complaining about rising costs, the burden of regulatory compliance and supply chain disruptions. The net result is they are in no mood to invest heavily in new supply when there is such an uncertain regulatory cloud hanging over their businesses. That’s inhibiting the non-OPEC+ supply response to higher prices. The Strategic Oil Reserve cannot be emptied twice, so that is an additional factor supporting prices.