US Patent 9347309 Cement plug location

The disclosure describes a system and a method for locating a cement plug within a wellbore. The system includes a signal transmitter mounted to the cement plug, a receiver at the opening to the wellbore, one clock positioned on the cement plug and in communication with the transmitter, a second clock which is synchronized to the first clock and in communication with the receiver, and a controller for triggering the transmittal of the signal.