Aren’t some oil fields essentially storage too?
I don’t agree with that character association. The oil flow out of the field is not varied except in extreme or upset conditions. And oil is never sent back into it.
“Arent some oil fields essentially storage too?”
Yes and no. There are a number of old oil fields which serve in some capacity as storage for the US Strategic Petroleum Reserve. These are mostly just used as storage and not much oil now is pumped into them. The amount is quite considerable at over 700 million barrels, making them in aggregate the largest oil storage in the world, and the amount of oil is bigger than any of the US’s remaining oil fields save a select few. Their key is the ability to drawdown very rapidly these amounts for domestic usage.
Generally, it is infeasible to reinject oil back into oil fields as too much would be lost in the process unless specialized provisions are made such as in the SPR fields.
Natural gas is much more common to be reinjected back into production gas fields to use as storage as there are definite cycles when usage is so great that insufficient supply would otherwise be available for heating and power generation.