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The University of Southampton
Clean Carbon

Detecting leaks from undersea gas pipelines, seabed methane reserves, and carbon capture and storage facilities

Undersea gas leakages (from both natural reservoirs and manmade structures) represent an environmental hazard on an immense scale. It is therefore vital that we know where they are and, once they have been identified, how they should be dealt with.

Finding the leaks - with a low cost solution

Professors Tim Leighton and Paul White have developed an invention that is 100x more sensitive than the current commercial systems used for detecting leaks from undersea gas pipelines. Also, their new technology can detect leaks from anywhere, whether from something man made, like a pipe, or from a natural source, like sea-bed methane leaks. Their ‘passive acoustic system’ for remote leak detection and quantification, has the added advantage that it is capable of long-term monitoring because of its low power requirements. Once the equipment is installed underwater, it can harvest energy from passing currents, driving mini turbines, so it will never need refuelling  The only equipment needed is underwater headphones (hydrophones) and these are readily available. The technique itself comes from a set of equations that can be used to instruct a computer on how to interpret the sounds picked up by the hydrophones in terms of the amount of gas released.

So what are these sounds?

When gas leaks occur underwater, bubbles are produced and as this happens, each bubble produces a note - recall the low notes in the bubbling noise made by scuba divers, for example. The smaller the bubble, the higher the note. So when a leak occurs, each bubble ‘sings’ its own note: it is like listening to a choir singing, where each person sings their own note, but just once. Some voice overlap, some do not. Therefore by analysing the sound we can work out how many bubbles are produced each second, and what size they are. That gives you the rate at which gas is being released into the water. It is particularly useful at detecting very small leaks at an early stage - which is an advantage as it allows something to be done about it before the leak grows bigger, releasing more gas.

Why do we need this technology?

  • A major technology for reducing the amount of atmospheric carbon is to pump carbon dioxide from the atmosphere into the vast empty chambers created beneath the seabed by the previous extraction from them of oil and gas for fuel. This technology is called ‘Carbon Capture and Storage' (CSS). Detection of any leakage from these storage facilities is important, because otherwise it would undo all the good work achieved in putting the CO2 down there in the first place. Early detection is important for two reasons: firstly, because a small leak is easier to fix than the large one it might well become if you leave it, and secondly, because leaks of CO2 could acidify the seawater and seabed in their vicinity and thus damage flora and fauna.
  • Naturally occurring reserves of methane in the seabed also release bubbles, but rising temperatures (as a result of man made climate change) could increase the rate at which natural methane escapes from the seabed. This could lead to an enhanced greenhouse effect, creating a vicious circle. Monitoring the rate of methane bubbling from natural reserves is therefore very important.
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