In this sense "barrel" is a unit of measure. The oil is physically in tanks in Oklahoma. When oil is delivered it stays in the same tank, but the ledger for the

In this sense "barrel" is a unit of measure. The oil is physically in tanks in Oklahoma. When oil is delivered it stays in the same tank, but the ledger for the tank contents are updated. Once delivery is made you are now on the hook for the storage costs - which are going sky high because there is no available storage inventory. You can default on your obligations to the storage company, but they will sell off whatever oil you hold to cover debts and then sue you for the rest. When the market is functioning correctly you end up paying for a few days of storage while the oil is diverted to a pipeline where you can extract it, or it is offloaded on to your train/truck/tanker/etc.