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The University of Southampton
Engineering

Research project: World's first experiment tests for leaks from carbon capture and storage seabed facilities

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Precis In 2010 Leighton and White (2012) published a method of detecting and quantifying the leakage of gas from Carbon Capture and Storage facilities in the seabed, using just the sound made by the escaping bubbles (called the ‘passive acoustic’ method below). Later that year the invention successfully detected leaks in the world's first controlled gas release field trial to test technologies for the detection of carbon dioxide leaks from Carbon Capture and Storage Facilities, in the sea of Scotland. This pioneering technology is now being deployed in a pan-EU Carbon Capture and Storage Project (March 2016) in the world’s first ‘real world’ deepwater controlled experiment simulating emission from a submerged carbon dioxide storage reservoir. The experiment is to take place in the North Sea, with the aim of further verifying the safety of offshore CO2 capture and storage (CCS). Small quantities of CO2 will be injected into mud on the seafloor in the North Sea, 100 kilometres north east of Aberdeen, Scotland. This site is in the vicinity of a depleted gas field and is a typical location that could be used for carbon dioxide storage. This first of a kind experiment, due to take place in 2018, will form part of a GB£13 million collaborative project led by the National Oceanography Centre at Southampton.

Background

To mitigate against the increase in manmade carbon dioxide in the atmosphere, and its effect on climate, strategies include capturing carbon dioxide from the atmosphere and storing it in depleted oil wells in the seabed. However it is vital to be able to detect leaks from such ‘Carbon capture and storage facilities’. In 2012 the world’s first experiment was undertaken to look at the impact of such leaks. Many organisations cooperated in this study to look at different aspects of a controlled test gas release from the seabed (click here for details), and the Leighton-White acoustic method successfully detected and quantified the leaks.

Details

The figure below shows the schematic diagram of the experiment: carbon dioxide from an onshore facility is injected via a pipeline into the seabed. Various sensors from a range of institutions were used to examine the effects of this. The ‘passive acoustic’ method was deployed to try to quantify the amount of gas leaking from the seabed into the water column using by listening to it using underwater microphones (hydrophones).

Schematic of the experiment (Source: www.bgs.ac.uk)
Schematic of the experiment

The ‘passive acoustic’ method not only detected the leakage of gas from the seabed, but also accurately quantified the gas flow rate from the leak, continuously over many days (see the orange plot in the figure below). This invention measures the flux of carbon dioxide bubbling up from the seabed (orange plot, with a 24 hour rolling average overlying it as a blue line), showing it varies with tide (upper plot).

Our inventions measures carbon dioxide leaks from the seabed (orange line) – from Nature Climate Change (doi: 10.1038/nclimate2381)
Gas flux plot

The real power of the ‘passive acoustic’ method is shown by the fact that it monitored continuously and cheaply for many days (for example allowing the correlation with tide to be revealed). This is far cheaper than the more expensive system of sending divers down to collect gas in bottles – this method produced a measure of the gas flux only for the short time the divers were down (as shown by the X on the plot.

The divers therefore could not pick up the variation of the gas leak rate with tide that the acoustic invention detected. Plans for currently underway for further deployments. Click here for media stories on this.

Publications

Leighton, T.G. and White, P.R. (2012) Quantification of undersea gas leaks from carbon capture and storage facilities, from pipelines and from methane seeps, by their acoustic emissions, Proceedings of the Royal Society A, 468, 485-510

Related research groups

Acoustics Group
Signal Processing, Audio and Hearing Group
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