Plug tracking using through-the-earth communication system

A releasable object for release into an oil and gas wellbore, the releasable object comprising:

• a body configured to sealingly engage an inner wall of a piping system to separate a first fluid from a second fluid;
• and
• a very low frequency (VLF) transmitter carried by the body,
• wherein the body is a plug comprising an elongated tubular body having a first end and a second end with a bore formed therein which allows fluid to pass therethrough, the transmitter being mounted in the bore.

A method for tracking the position an object released into a wellbore piping system, the method comprising:

• positioning a first very low frequency (VLF) signal system along a surface of the earth above a formation in which a wellbore is formed, wherein the first VLF signal system is coupled to the surface and the wellbore contains a piping system disposed therein;
• releasing a releasable object into the piping system, wherein the releasable object sealingly engages an inner wall of the piping system to isolate a first fluid from a second fluid;
• transmitting a VLF signal through the earth between the releasable object and the first VLF signal system;
• and
• determining the position of the object in the wellbore based on the transmitted VLF signal.