With a metal well casing would not there have to be an uncleared fault ?
Actually, no. See, the amount of current in the earth between the well casing and the ground connection at the local supply transformer is current subtracted from the service neutral conductor.
If all of the occupancy load unbalance current (neutral current) were
only in the service neutral conductor, then the load created net magnetic field around all of the service entrance conductors will be zero.
Except. . . and this is a real wild card. . . for the PoCo primary side neutral currents. And, since most PoCos have their distribution neutral solidly connected to the customer neutral because of the common ground at the pole or pad that the transformer is at, a neighbor, on a different transformer, with a failed neutral, under certain conditions, can have part of its unbalance current coming through this occupancy's neutral to get to the well casing.
Pulling a meter from the meter base won't interrupt all of the neutral current.
Other PoCo primary side currents will come from the distribution system currents, as well as the very Earth, itself.