Acoustic monitoring system for subsea wellhead tools and downhole equipment

A method and apparatus for remotely monitoring the condition (e.g. operative state or relative position) of a subsurface tool/piece of equipment 14 by detecting acoustic emissions from the tool/equipment 14. The acoustic emissions are transmitted through an acoustic transmission medium (e.g drill string 12) to which the tool/equipment 14 is attached, and detected by a transducer in monitoring device 26 at surface level. The monitoring device 26 may be temporarily or permanently attached to the transmission medium. The acoustic emissions are either inherently generated by the use of the tool/equipment 14, or they are generated by a transducer 32 incorporated into the tool/equipment 14 that generates acoustic transmissions characteristic of the tool/equipment 14 conditions of interest. Signals from the detection transducer may be amplified, filtered, counted and the count supplied to a user display or data logger.