This paper reviews techniques for leak detection monitoring on subsea pipelines. Five established leak detection techniques and one emerging technique are reviewed. In each case the area of applicability of the technique is considered.
The capacity of each technique to identify the location of the leak is also considered.
The objective of pipeline integrity monitoring is to ensure that a pipeline continues to function safely. For subsea pipelines on the United Kingdom Continental pipelines on the United Kingdom Continental Shelf leak detection is regarded as part of an overall pipeline integrity monitoring philosophy. The Guidance Notes for philosophy. The Guidance Notes for Submarine Pipelines refer to the Institute of Petroleum Model Code Part 6, Supplement Pipeline Safety Code. Pipeline Safety Code. The Pipeline Safety Code sub-divides integrity monitoring into three sub-activities:
There is considerable overlap between the activities in the above list. While this paper primarily considers leak detection paper primarily considers leak detection most of the techniques reviewed are applicable to at least two of the above activities.
Leak detection is only one aspect of an overall pipeline integrity monitoring philosophy. This philosophy should philosophy. This philosophy should incorporate suitable procedures regarding the operational response required following leak detection. The efficacy of these procedures should be checked regularly with procedures should be checked regularly with exercises incorporating simulated leaks.
In determining the operational response to a leak knowledge of the leak site can be very important. Accordingly this paper also addresses the problem of leak location.
With respect to subsea pipelines a leak can be considered as an undesirable egress (or ingress) of fluid from the pipe. Associated with this egress will be a change in the physical and chemical environment outside or physical and chemical environment outside or inside the pipeline.
In order to identify this change it is necessary for the effects to propagate to the location of the relevant sensing equipment. Thus the propagation speed and the locations of the relevant sensing transducers will have a major influence on the "Time to Detect" a leak.
In general the strength of the physical/chemical effect will be dissipated physical/chemical effect will be dissipated or attenuated as the effect propagates. Thus the locations of the relevant sensing transducers will have a major influence on the minimum size of leak detectable.