Plug, System and Method for Testing the Integrity of a Well Barrier

A method for testing the integrity of a barrier in a well, by means of a system comprising:

• a well having a wellbore and a upper wellbore termination means;
• at least one of a mud circulation system and a mud conditioning system comprising means for transporting, cleaning or storing mud outside said wellbore;
• a barrier provided in the wellbore, the barrier having an upstream side below the barrier and a downstream side above the barrier;
• a tracer;
• a storage means for storing said tracer, the storage means being provided in at least one of a lower part of the barrier and below the barrier in the well;
• and
• a release mechanism for releasing the tracer from the storage means, wherein
• a pressure differential is established across the barrier for driving tracer from the upstream side to the downstream side of the barrier;
• the system further comprises a detector for detecting the tracer that has leaked through the barrier and into said mud the detector being arranged above the wellbore in at least one of the mud circulation system and the mud conditioning system;
• the method comprising:
• releasing the tracer from below the barrier,
• establishing a pressure gradient across the barrier;
• and
• monitoring a concentration of tracer in the mud by detectors arranged in at least one of the mud circulation system and the mud conditioning system.