The authors have developed an active acoustic Automatic Leak Detection Sonar (ALDS) designed to detect hydrocarbon leaks (mono and multi-phase oil and gas) at significant ranges, allowing coverage of wide areas from a single sensor. The system's single subsea sensor offers 360 degree continuous coverage providing automatic, robust detection and localisation of any leak, followed by an alert within tens of seconds of a leak developing.

This paper provides a case study of an experimental programme where the system was trialled in deep water (2000 m) at the Thunderhorse field in the US Gulf of Mexico. We will describe the principles of operation and theoretical performance of the system and compare this to the actual performance in-situ where simulated oil and gas releases were used to identify the system performance limits. Results will be provided for a simulated single phase oil leak of approximately 100 barrels a day and gas detection leaks of as little as 1 litre per minute. The trials include detections with subsea infrastructure (wellheads, manifolds etc.) between the leak location and the sensing head.

The results demonstrate the efficacy of active acoustic leak detection over ranges in excess of 600 m from the sensing point, as well as good discrimination of leaks against other acoustic targets resulting in an exceptionally low false alarm rate.

Finally learning points from the trials regarding the CONcept of OPerationS (CONOPS) for permanently deployed leak detection systems will be discussed with a description of how an active acoustic leak detection system can best be implemented in a variety of scenarios during the life of a field, from exploratory drilling through to production and decommissioning. Particular reference will be made to how this applies to already producing and planned Brazilian field devlopments addressing retrofit and new build requirements.

ALDS can be used as a regulatory tool but can also bring value to operators by identifying and enabling early intervention on the small leaks which often prefigure large hydrocarbon releases, reducing the likelihood major environmental damage and protecting reputation.

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