The devil is in the details and until we get the specific information on the pressure drop, we are onyl speculating.
The first question is where did the pressure drop occur? If we are talking about a pressure drop within the well, then as Art stated, if you have a large compressor tank and are slowly bleeding off a small amount of air, it will take a while for the pressure drop to occur. The same goes for the A5 well, if highly fractured and a low flow rate, it will take a while to see a pressure drop.
If we are talking about seeing a pressure drop in the other Ant. pressure monitoring wells and it took 2 days to see the pressure drop, this is good in that it shows Ant. is a large connected basin. If a pressure drop does not occur in the other wells, it shows that we gave a basin that is not connected. This would be very bad, at least short term for the stock.
Good luck longs.