Achieving accurate leak detection

Pedro Barbosa, Fotech, UK, a bp Launchpad company, reviews the various challenges hydrogen presents, and discusses how distributed acoustic sensing (DAS) provides an accurate and faster leak detection solution for smaller leaks.

he oil and gas industry is currently undergoing a major shift as companies look to reduce emissions and achieve net-zero by 2050, or earlier. As well as turning attention towards sustainable energy sources such as wind and solar as part of this energy transition, oil and gas companies are investigating clean hydrogen – produced using renewables, nuclear or fossil fuels with carbon capture – as an alternative fuel source. Indeed, it is anticipated that demand for clean hydrogen will grow fivefold by 2050, avoiding up to 80 Gt CO2 emissions.1,2

There are many hydrogen projects being initiated worldwide, however, there are approximately only 1600 miles of hydrogen pipeline infrastructure that currently exists in the USA compared to 305 000 miles of natural gas pipelines, and 190 000 miles of liquid fuel pipelines.3 According to the Hydrogen Council, there have been more than 520 large-scale projects and 90+ GW of electrolyser production capacity announced globally.4 As part of these projects, companies are building new pipelines while transmission system operators (TSOs) are looking at repurposing existing natural gas pipelines. As the popularity of hydrogen increases, it becomes vital that the pipeline network is robust with systems in place to transport the gas safely. Transporting hydrogen gas is no easy feat, and operators face new challenges not seen with the transport of oil and natural gas.

The challenges of transporting hydrogen

Hydrogen is highly flammable Hydrogen presents a higher risk of explosion compared to other fuels because it has a very high energy content per mass. For example, the energy content is approximately

three times higher than petrol, which means it has a lower ignition energy, so it can ignite more easily.5

High risk of leaks The size of a hydrogen molecule is smaller than any other gas. As such, it diffuses more easily in materials than other common gases at equivalent pressures. This makes it prone to leaking easily through cracks or poor joints in storage and transportation systems.6

Hydrogen is generally non-corrosive and does not react with the materials used for pipelines. However, at certain temperatures and pressures it can diffuse into a metal lattice causing ‘hydrogen embrittlement’.7 In particular, hydrogen has the potential to embrittle the steel and welds used to fabricate the pipelines, which can damage their integrity.

Environmental issues The environmental benefits gained by introducing hydrogen as a mainstream fuel would quickly be offset if there were any leaks. According to the UK government’s policy paper ‘Atmospheric implications of increased hydrogen use’, hydrogen leakage will affect atmospheric composition, ultimately negatively affecting air quality, and has an indirect warming effect on the climate.8

Reducing the risk of leaks For hydrogen to be adopted as a major energy source, it’s clear that eliminating the risk of leaks should be a priority. To ensure pipeline safety and integrity, they need to be designed and maintained to the highest standards. This includes robust ventilation coupled with leak detection systems that can identify the very smallest of leaks. That’s where advanced monitoring technologies such as DAS have a role to play.

Typically, monitoring techniques, such as computational pipeline monitoring systems, have been used to monitor for leaks in existing oil and gas pipelines. However, since they infer the presence of a leak by computational modelling, they tend to have long detectability times and low sensitivity to small leaks. DAS, on the other hand, can alleviate these issues.

A closer look at DAS DAS technology, such Fotech’s LivePIPE II solution, turns a fibre optic cable running alongside a pipeline network into thousands of vibration sensors by using photonics. It then detects any disturbances along the length of the pipeline.

The technology sends thousands of pulses of light along the fibre optic cable every second and monitors the fine pattern of light reflected back. When acoustic or vibrational energy – such as that created by a leak or by integrity threats including third-party interferences or geo-hazards – creates a strain on the optical fibre, it changes the reflected light pattern. By using advanced algorithms and processing techniques, DAS analyses these changes to identify and to categorise any disturbance.

Each type of disturbance has its own signature and the technology can tell an operator, in real-time, what happened, exactly where it happened, and when. DAS delivers advanced monitoring DAS is ideal for monitoring hydrogen in pipelines for a number of reasons:

Continuous real-time monitoring DAS provides live monitoring around the clock, 24/7, and on pipelines spanning thousands of kilometres. That means operators are immediately alerted when an incident has occurred, even in the most remote locations, so they can take remedial action to prevent major incidents.

High accuracy DAS accurately locates disturbances to within 10 m, as well as identifying multiple events and their locations simultaneously. It enables operators to go straight to the site of incident, dig once, and thus minimises repair costs.

Additionally, advanced AI and machine learning included in the newest DAS technologies filter out background noise and non-threat activity, and calibrate responses for high-risk and low-risk zones. This reduces false alarms and ensures operators receive the exact information needed to make informed decisions.

Quick detection of small leaks DAS can detect gas leaks from tiny orifices as small as 1 mm, and alert operators within seconds. The technology is able to detect vibrations caused by gas being forced through small pinholes and cracks that would otherwise remain undetected.

Hydrogen as the fuel of the future Hydrogen is hotly anticipated as a more sustainable fuel source and interest in this gas is rapidly growing. Future predictions suggest that by 2035, hydrogen, electric power and synfuels will represent more than 30% of the global energy mix, and by 2050 it will be as much as 50%.9

However, hydrogen’s inherent properties mean it is especially hazardous to transport and therefore careful consideration needs to be taken when designing pipelines. Robust strategies and technologies for minimising leaks, such as DAS, need to be implemented if hydrogen is to be accepted as a valuable alternative fuel.

References

1. www.mckinsey.com/industries/oil-and-gas/our-insights/global-energyperspective-2022 2. hydrogencouncil.com/en/ceo-coalition-to-cop26-leaders-hydrogen-tocontribute-over-20-of-global-carbon-abatement-by-2050-strong-publicprivate-collaboration-required-to-make-it-a-reality 3. www.energy.gov/eere/fuelcells/hydrogen-pipelines 4. hydrogencouncil.com/en/ceo-coalition-to-cop26-leaders-hydrogen-tocontribute-over-20-of-global-carbon-abatement-by-2050-strong-publicprivate-collaboration-required-to-make-it-a-reality 5. www.eia.gov/energyexplained/hydrogen 6. www.hyresponse.eu/files/Lectures/Safety_of_hydrogen_storage_notes. pdf 7. www.hyresponse.eu/files/Lectures/Safety_of_hydrogen_storage_notes. pdf 8. www.gov.uk/government/publications/atmospheric-implications-ofincreased-hydrogen-use 9. www.mckinsey.com/industries/oil-and-gas/our-insights/global-energyperspective-2022