Global Oil & Gas Subsea Umbilicals, Risers and Flowlines (SURF) Market 2021- brochure
Subsea Pipeline and Installations Leak...
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a report by Chris Teal Director, Neptune Oceanographics Ltd The Need For Subsea Leak Detection Globally, the environmental aspects of subsea pipeline systems are of major concern and are increasingly so as regulatory authorities around the world become less tolerant of potential releases of polluting material into the marine environment. The concerns are of particular relevance to subsea pipeline installations and, in this respect, the ability to detect and locate any leakage of gas or oil to the surrounding waters is of paramount importance. Historically, two main methods of subsea leak detection have been used for leaks where obvious visual signs of large leaks such as bubbles, large clouds, etc. are either not present or have failed to locate the problem. The two main methods used are in situ fluorometric measurement and passive acoustics, which ‘listens’ for ultrasound created by fluid leaking under pressure. Neptune Oceanographics Ltd is a leader in the field of detection of leaks in subsea pipelines, risers and control systems and has made significant technical advances in the traditional techniques mentioned above. In addition, Neptune Oceanographics is constantly striving to develop systems that are more efficient in terms of cost, detection success rate and the effect on the environment. Two such new developments are described later in this article. Fluorometry To date, the most successful method of detecting leaks has been the use of fluorescent dyes detected by ‘black light’ (unfiltered ultraviolet [UV] light) with visual observation either directly by diver or by underwater camera. The major problem with this method is that the dye concentration has to be high (see Figure 1) to allow visual observation. Also, general visibility must be good. Deploying submersible fluorometers that send data up to the attendant vessel providing a realtime visual display has, to a large extent, solved these problems. These submersible fluorometers are very sensitive and will detect dye at concentration so low as to be invisible to the naked eye or underwater camera. The commonly used dyes, such as fluorescein, are becoming less favoured as a means of detection in that they cannot meet the zero discharge of environmentally harmful pollutants now being sought. Increasingly, regulatory authorities around the world are asking the oil and gas industry to find ways of detecting leaks that do not require the introduction of these additional potential pollutants. Where subsea control systems are concerned, the control fluids normally have fluorescein dye, or similar, as a component solely for the purpose of leak detection. As with all control systems, leakages through seals, flanges, etc., do occur and, therefore, means of detection and location are essential. To meet the requirement of phasing out fluorescein, other dyes, that have been tested to demonstrate compliance with the latest legislation, have been developed. One such dye is a component of Castrol Offshore’s new ‘Transaqua’ water-based control fluid. This dye fluoresces in the same manner as fluorescein but at different wavelengths. Whatever means of observation is used to detect fluorescence, dye is still required and it will, Subsea Pipeline and Installations Leak Detection BUSINESS BRIEFING: EXPLORATION & PRODUCTION: THE OIL & GAS REVIEW 2003 – VOLUME 2
