You can never completely deplete a field.
True that, but if you can't produce it and turn a profit anymore, it's considered depleted.
Lots of older wells are P&A'ed because of pressure drop off or watering out and no amount of remedial work will help that zone produce again.
Had that happen on a well that produced on my property for over 30 years (part of Chacahoula oil and gas field).
They ran a TDT (Thermal decay tool), found that zone had watered out totally, but found another zone 2000ft. up the hole they had missed when equipment wasn't as sophisticated, plugged the old zone, perforated the new zone and cha-ching, viable well again, but different zone.
The outfit I worked for did a lot of work of that type on older *played out* wells in the Chacahoula field.