Root causes of hydrocarbon leaks on offshore petroleum installations

Hydrocarbon leaks on offshore installations may result in severe consequences to personnel, to the environment and to assets. In order to prevent such leaks, it is crucial to understand their root causes. The objective of this paper is to study the circumstances of hydrocarbon leaks on the Norwegian continental shelf (NCS). In the study, all reported hydrocarbon leaks from process inventories on all offshore installations on the NCS, with an initial leak rate higher than 0.1 kg/s in the period 2008–2014, have been considered. This includes 78 hydrocarbon leaks, of which about 60% have occurred during manual intervention on normally pressurized systems. The dominating activity when leaks occur is preventive maintenance. A significant fraction of the leaks occur during the preparation for maintenance; such a preparation is typically carried out during the night shift. About half of the leaks are associated with wellhead area and manifolds, separation and compression systems. A substantial fraction of the leaks can be associated with verification faults, dominated by the failure to comply with procedural requirements that are needed to carry out independent verification. •Almost 60% of the leaks over long time have been associated with manual intervention.•Almost one third of the leaks occurred in association with preventive maintenance.•Maloperation of valves during isolation work is the main cause in the last years.•Break-down of isolation systems during maintenance is also a frequent cause.•Failure to perform verification is the most frequent contributing factor.