Sponsored Content: Track down greenhouse gas leak sources: Using tunable laser technology to detect methane emissions in the field
Methane gas leaks are a growing problem in the USA, which is estimated to have 3.2 MM wells that are either orphaned, with no owner or operator, or abandoned by identified owners1.
ABB was commissioned by the University of California Berkeley (Lawrence Berkeley Laboratory), funded by the California Energy Commission, to perform measurements over an abandoned gas well with HoverGuard 60 miles north of San Jose.
The goal was to demonstrate the effectiveness of ABB’s system for measuring gas leaks in the wild. ABB deployed its drone-based HoverGuard detection system as the main analysis method.
The company also used its MicroGuard (hand portable) and MobileGuard (vehicle based) to demonstrate the effectiveness of each system and gather data about how they operated in a real-world case.
HoverGuard was able to find and characterize the suspected leak but also found another, much larger leak. This second, larger leak was previously unknown, originating far from the road but having a significantly larger emission rate.
Detection of methane gas emissions
Natural gas remains an important part of the energy mix and it is seen by many as a valuable transition fuel for electricity generation between highly polluting coal and more permanent non-fossil energy sources such as wind and solar.
It also plays an important role in balancing out demand when renewable sources cannot operate effectively. Although demand for gas will slow in the coming years, consumption by 2024 will be higher than the IEA considers ideal if we are to meet the net-zero targets set for 20502.
Natural gas primarily consists of methane, together with lower percentages of other hydrocarbons. It also contains water, carbon dioxide, nitrogen, oxygen, and some sulfur compounds.
Carbon dioxide gets most of the attention for its atmospheric warming potential, yet methane is the second main greenhouse gas and is of increasing concern. Despite having a shorter lifespan than CO2, methane’s heating potential is up to 84 times greater over a 20-year period.
In 2019, atmospheric methane reached record levels, at over two and a half times the level of pre-industrial times. Major sources of methane emissions include manure, coal mining, landfill, livestock, and natural gas, with natural gas production and distribution accounting for the majority, at over 30 percent of total emissions.
Government and environmental agencies have recognized that methane emissions need to be curbed. This is the goal of the Global Methane Pledge. Signed at COP26 by over 100 countries, this pledge aims to reduce methane emissions in the atmosphere by 30 percent by 2030.
It has been estimated that this reduction could achieve at least a 0.3°C reduction in global warming by 2040. Using natural gas more efficiently is a way to reduce its environmental impact and the IEA recommends that the gas industry act quickly and effectively to reduce needless methane emissions.
As well as meeting environmental concerns, the ability to quickly detect and fix a gas leak also makes good sense from an economic and safety perspective. Gas leaking from pipelines represents the loss of billions of dollars of revenue every year, from direct product loss and the effort and costs involved in replacing it.
Data from the US government’s Pipeline and Hazardous Materials Safety Administration (PHMSA) show that from 2000-2019, 686 serious incidents occurred on gas pipelines, accounting for 253 fatalities and 1,111 injuries3.
This means that operators of gas wells and pipelines need to become better at detecting gas leaks from their facilities. As well as cutting monetary losses from the escape of gas into the atmosphere, they will also be helping to reduce methane’s contribution to global warming.
To encourage this, an effective, efficient, and rapid method of detecting leaks is needed. So far, the traditional methods used to detect gas leaks have not met these criteria. As well as being slow, they have lacked the accuracy and sensitivity required and have particularly lacked the ability to detect leaks efficiently and reliably.
These techniques rely on handheld analog detectors that technicians need to carry across the suspected gas leak area. The devices employed in these techniques need time to calibrate on site and also have a low detection rate, requiring users to walk slowly over the investigation area. Test data also needs to be added to systems manually, further increasing the time required to analyze a potential leak.
Recent technological advances have seen improvements in sensing, analytics, and mobile technology. These have allowed the development of improved techniques that perform significantly better than traditional methods.
These systems can detect methane from natural gas leaks at concentrations of 1 part per B (ppB).
ABB is one of the pioneers in this field and has produced a range of gas detection applications based on its LGR-ICOS technology.
The latest variant, known as off-axis integrated cavity output spectroscopy (OA-ICOS), uses a tunable laser that produces light at a selected wavelength to interact with the methane and ethane gases that need to be detected. This can achieve a sensitivity more than 1,000 times higher than conventional technologies and detect leaks at distances of around 100 meters.
The laser enters a highly reflective mirrored cavity, where it is reflected thousands of times before exiting onto a photodetector. This results in the laser following a very long optical path of many kilometers, producing an increased measurement sensitivity, and producing strong absorption of the infrared light by the gas.
Changing the wavelength of the laser allows the gas concentration to be measured with high precision and accuracy. The method detects single parts per billion of the targeted gas. This ensures that variations in atmospheric concentrations can quickly be measured from long distances, a feat that other technologies struggle to emulate.
The Nurse Slough Road survey
Why the survey was conducted. The number of orphan oil and gas wells poses a major risk to both the climate and public health. These wells are often abandoned by companies that leave the site after fraudulent activity or falling into bankruptcy, allowing the wells to leach methane into the atmosphere.
This is a growing problem. For example, it has been estimated that the number of abandoned wells in Texas and New Mexico could rise by nearly 200 percent in the next few years. Clean-up costs are expected to run into the hundreds of millions or even billions of dollars nationwide, yet both the true cost and the true number of abandoned wells remains unknown.
The US Environmental Protection Agency (EPA) estimates that the number of unplugged orphan wells could be as high as 2.1 million across the United States.4
To investigate the effectiveness of ABB’s detection technologies in actual site conditions, the University of California Berkeley (LLBL) asked ABB to perform measurements over an abandoned gas well 60 miles north of San Jose with HoverGuard. On March 23, 2021, ABB surveyed an artesian well in Solano County, California, located on private property off Nurse Slough Road. Located between several old oil exploration fields, the site includes a marsh that borders the public road. ABB deployed HoverGuard as well as MicroGuard and MobileGuard to demonstrate how they could be used in real-world situations to discover and analyze methane leaks from wells.
Survey methodology One of the goals of the March 2021 survey was to follow up on a previous survey conducted in February 2021 that indicated a much larger and previously unknown source further into the marsh. This source was not investigated during the first visit due to the challenging terrain’s difficult access.
However, the team thought the site deserved further investigation to verify methane source extent and release characteristics. In the March survey, ABB examined the site with three commercially available ABB technologies: MobileGuard, HoverGuard and MicroGuard. The method adopted was similar to that employed during the first survey. The vehicle based MobileGuard conducted a number of drive passes along the adjacent road, while HoverGuard investigated from the air, the aerial survey was carried out using encircling lawnmower patterns at two altitudes, and a fence-line pattern.
The MicroGuard investigation differed because the follow-up survey’s primary goal was to locate a larger, previously indicated emission that was suspected of existing further into the marsh. This location was extremely difficult to access because of the terrain, which consisted of tall marsh reeds, deep water, and mud. Because of this, the MicroGuard investigation used indications from the UAV as a starting point, but then followed an ad hoc path based on walkability.
The ABB products deployed HoverGuard performed four separate surveys of approximately 20 minutes each using the same survey patterns as in the February visit. As with the initial survey, HoverGuard detected the artesian well, together with a large, previously un - known emission source located deeper in the marsh.
On the second day of the survey, additional smaller emission sources were detected due to the lower winds. In addition to the UAV-based inspection, ABB per - formed a follow-up vehicle-based, MobileGuard investigation. Because the wind conditions were coming from the same consistent southerly direction as the first survey, the UAV inspection could access downwind locations.
The large leak was completely inaccessible by conventional vehicles, while the artesian well is only sampled on the edge of the emission plume.
However, MobileGuard was able to detect the nearest source (the artesian well) because the southerly wind dispersed some of the emission to the roadway. With its high sensitivity, MobileGuard could identify the emission and estimate its location and flow rate. Several minor sources north of the levee were easily detected. In a final stage, ABB conducted a pinpointing operation using the data collected from HoverGuard.
This focused on locating the hard-to-reach large emission source at an unknown location in the marsh. As well as rapidly locating the artesian well, MicroGuard was also able to locate several other sources deeper into the marsh. The largest of these was inaccessible during the first survey but was reached in the second survey in March 2021.
Key findings During the March investigation, ABB surveyed with HoverGuard, MobileGuard and MicroGuard and each system was able to detect gas emissions from the artesian well rapidly and accurately. MicroGuard was able to identify the previously indicated large leak found 50 meters farther out in the marsh than the artesian well.
Estimated methane emission rates determined by HoverGuard and MobileGuard largely agreed with a chamber flux measurement that uses a sealed tent to measure methane concentrations. They were also well within the margin of error, demonstrating their ability to quantify and rank the severity of the source.
The difficulty in detecting leaks of this magnitude with older technologies increases uncertainty on the estimates of methane emissions from the large number of uncapped and undocumented wells throughout the USA.
Previous optical sensing methods based on aircraft-based sensors failed to detect any of the emissions at the site, even the large source. Most, if not all, flight-based methane detection systems measure the absorption or scattering by the methane column density or the product of gas concentration and effective optical path length.
Since the methane was effectively spread over a wide area, the column density along the line of sight remained low but the total emission rate was not small.
ABB’s products for gas leak detection, mapping, and quantification MobileGuard ABB’s MobileGuard system is a vehicle-mounted system that enables accurate natural gas leak detection while driving.
The system makes use of an LGR-ICOS methane and ethane gas analyzer as well as an ultrasonic anemometer for measuring wind speed and a Global Navigation Satellite System (GNSS) for measuring location.
Using ABB’s innovative mapping and quantification algorithms, the MobileGuard system locates, maps, and quantifies the size of pipeline leaks from a moving vehicle far from the emission source. The system takes multiple measurements per second, performing accurate leak surveys while driving at speeds of up to 88 km/h (55 mph).
This allows surveyors to cover 10-25 times more land area per minute than with traditional methods. The analyzer measures both methane and ethane concentrations, allowing it to distinguish between pipeline gas or naturally occurring methane and thus virtually eliminates false positives. The MobileGuard system analyzes data locally and presents geospatial maps of all measured parameters in real-time. Data and analyses can be securely relayed to cloud storage for easy sharing, archiving, and further analysis.
HoverGuard
When methane leaks from a pipeline, it mixes with the air, subsequently decreasing in concentration as it moves further away from the leak site. Detecting this methane can be achieved by passing an airborne analyzer through the diffused methane, allowing its concentration levels to be calculated quickly.
ABB’s HoverGuard is a UAV based solution that offers a fast, low cost and safe method for identifying potential leakage points. It also allows access to areas that would not otherwise be accessible either by foot or by a vehicle, such as bridges, high-rise buildings and areas posing a significant risk to human health and safety.
HoverGuard also offers a much less costly alternative to aircraft-based analyzers and can operate much closer to the ground and leak sources. By enabling the drone to sample the air at a rate of five times per second as it flies, this approach offers advantages over other techniques.
Most importantly, it offers greatly enhanced accuracy over laser-based systems using a scattered or reflected laser beam. The speed with which data can be gathered without compromising accuracy means that the drone can detect, locate, and estimate the size of natural gas leaks while covering 10-15 times more land area per minute than traditional methods.
Additionally, with its extremely sensitive technology and fast response rate, it can quickly detect leaks more than 100 meters (328 ft) from their source.
MicroGuard
MicroGuard uses the same ultrasensitive detector technology as the MobileGuard system but is optimized for being carried by technicians conducting surveys on foot. The solution consists of an LGRICOS gas analyzer, backpack, ruggedized tablet with GNNS capability, innovative analysis software, and a custom-designed sample wand.
The MicroGuard system enables walking surveyors to easily and accurately pinpoint natural gas leaks within minutes. Its software generates comprehensive digital reports of the survey, which can be shared immediately and securely.
Conclusion
Methane leaks from abandoned gas wells are a growing problem, both in the USA and globally. Detecting this potent greenhouse gas is a key priority if the world is to achieve its ambitions of slowing the rise in global warming. Assessing the accuracy of ABB’s laser-based techniques and the practicality of various mounting systems was the aim of the project to detect leaks at a site bordering Nurse Slough Road in California5.
ABB was able to demonstrate that its solutions worked effectively in field conditions. HoverGuard detects and localizes large, small, and hidden leaks that other technologies cannot.
The tests also proved the ability of MobileGuard to find and quantify leaks easily. MicroGuard was also used and tests showed that it can pinpoint leaks quickly, no matter where they are.
The solution can be used to quantify leaks accurately, in concert with a controlled tenting strategy. All the methods made use of ABB’s laser-based technology (OA-ICOS) that simultaneously measures methane and ethane gas with a sensitivity over 1,000 times higher than conventional technologies and can detect leaks at distances over 100 meters from the source.
References
1. https://www.nrdc.org/stories/millions-leaky-and-abandoned-oil-and-gas-wells-are-threatening-lives-and-climate
2. https://www.iea.org/news/natural-gas-demand-growth-set-to-slow-in-coming-years-but-strong-policyactions-still-needed-to-bring-it-on-track-for-net-zero-emissions
3. https://www.phmsa.dot.gov/data-and-statistics/pipeline/pipeline-incident-20-year-trends
4. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks
5. Yingqi Zhang, Veronica Rodriguez Tribaldos, Donald W. Vasco, Barry M. Freifeld, William Foxall, Kang Wang, Roland Burgmann, Brian Leen, Doug S. Baer and Curtis M. Oldenburg. 2021. Monitoring Report for an Integrated Risk Management and Decision-Support System (IRMDSS) for Assuring the Integrity of Underground Natural Gas Storage Infrastructure in California. California Energy Commission.
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