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Subsea leak detection 2011, Stavanger

3 November 2011, Stavanger

The Norsk olje og gass/PSA Leak detection seminar was held on 3rd November 2011 and over 70 people attended representing operators, regulators, Subsea EPC suppliers and vendors. At the seminar 16 presentations were made and most of these are included.

To large extent the objectives of the seminar were achieved, and to summarise the outcome, a number comments are made against each of the three objectives:

  • To communicate the approach being taken by regulators to improve environmental practices subsea

- Regulators are very supportive of permanent SSLD as a part of an overall environmental management strategy for subsea projects  and DNV RP-F-302 provides a good basis for their application

- Klif indicated that use of BAT ( best available technology) implies mandatory use of SSLD and emphasized the importance of rapid leak detection

- PSA indicated that Hydrocarbon leak incidents from subsea equipment are less than 4 per year, though between ’97 and ’09, 5 incidents have been classes as serious

- Due to their immaturity, SSLDs are not yet classed as a “safety” system requiring automated shutdown in the event of a positive detection

- Overall use of SSLD should be included in the overall Env. risk assessment and this was well demonstrated in the Goliat and Yme presentation

- BP have chosen on an HP development in the GOM, to deploy an active acoustic LD system which will shortly be commissioned and could be used elsewhere in BP

  • To share information and experience with developments in continuous  Subsea Leak detection, their potential and limitations

- Statoil has deployed Passive Acoustic (PA) SSLDs on Vega but have experienced 5 false alarms. Further commissioning to calibrate performance is planned end 2011

- On Tordis PA SSLDs have been effective in condition monitoring of subsea pumps as an adjunct to other information sources.   The installation has confirmed the importance of high speed data links to enable better monitoring of signals and calibration.

- After a number of challenges, Ormen Lange PA SSLDs are now operating and have been commissioned using simulated/recorded leaks.  A number of upgrades and fixes are still required but they should be fully operable in 2012.

- Presentations were made by the major suppliers – Franatech ( Their new TDLS-CH4 deep water Methane detector tool should now remain stable for 10 years) – Reson ( Active Acoustic as proven at Sintef, is a very effective tool but requires more power than PA, it can cover a wide area and position leaks accurately), Phaze (capacitance detector , the most widely used SSLD tool is used in conjunction with a sealed or partially sealed cover and perhaps in future with a control release valve), Bjørge Naxys ( Most widely used and mature PA detector, with improved reliability following extensive testing. Also available is the cheaper SALD  - single point ALD),  Biota Guard ( able to use captive mussles or other deepwater creaturs as indicators of pollution, through well understood stress indications), Aquadyne ( long history in subsea leak detection and hydrocarbon profiling and ready to deliver/ integrate best solutions).     

- The Goliat project will use a combination capacitance and SALDs  linked into the control system. The design is based on RP-F-302 and uses 3 SALD per mainfold and 1 Phase detector per well.

  • To identify relevant organisational and technical gaps and outline actions that take the industry forwards

- Technical gaps that exist at present, as covered by FMC – The FMECA process should be routinely used in design eg. a dead sensor indicates no leaks!  Design life is still unproven; qualification tests/ range / reliability etc are poorly defined; the signal chain has too many interfaces and risks loss of signal; commissioning process and validation testing still not formally included in standards or implemented properly; DNV RP-F-203 is not sufficiently prescriptive for sensors;  we need more LD alternatives and suppliers as it seems wise to use two technologies at each location.

- Organisationally,  Operators are not yet confident in the signals from their SSLDs. This may be a result of ineffective commissioning ( no-one knows the upper or lower limits of their sensitivity)  and ongoing validation is not always implemented. 

- However, more SSLDs are being deployed and leak statistics indicate that some positive leak detections will occur in the next few years.    That will quickly change their perceived value.  Routine use of acoustics for condition monitoring for subsea equipment is also gaining support.

- The pace of design/ software/ comms improvements is now accelerating This indicates that this technology has moved beyond infancy, but is still someway short of maturity.

- There is an ongoing need to share industry experience in this area.

There was a consensus that this event should be repeated again in 3 years  - in 2014

Norsk olje og gass AND PSA thank all those who attended and particularly those who gave presentations.


David Llewelyn

Norsk olje og gass Subsea Installations Network Facilitator