Methane Leakage Research Articles

Highly Uncertain Methane Leakage from Oil and Gas Wells in Canada Despite Measurement and Reporting.

Leakage of fluids from oil and gas wells is a source of the key greenhouse gas methane, and presents environmental risks, including groundwater contamination. A loss of well integrity can result in fluid leakage into the annular space between subsequent well casings (which is often vented to the atmosphere) or into the surrounding subsurface. In Canada, industry reporting on well integrity is often incomplete, leading government inventories to disagree on emission magnitudes. In this study, we model wellbore methane emissions using industry data in British Columbia and Alberta, Canada, finding that differing model assumptions to handle unclear/missing data have a strong influence on estimated emissions. Considering estimates derived from industry reporting and from independent measurement, wellbore emissions in the two provinces range anywhere from 23 to 176 kt of methane, representing 1.7-11.4% of their upstream sector methane emissions. Further, finding over 130 examples of measured leaks seemingly missing from industry reporting, we conclude that wellbore emissions, groundwater contamination, and broader environmental risks are underestimated. We provide recommendations to improve well integrity tracking through data quality assurance measures and increased testing. Finally, we find that ongoing optical gas imaging camera surveys could be an effective tool to augment wellbore testing requirements to minimize industry burden.

Global determinants of methane emissions in OECD countries: A dynamic panel approach

Methane (CH4), an often-overlooked greenhouse gas (GHG), has a significant impact on the environment. Although it receives less attention than carbon dioxide (CO2), it is the second most important GHG in terms of its ability to trap heat in the atmosphere. Few studies have analyzed the determinants of CH4 emissions, especially those from the energy sector. Therefore, this study provides relevant information on the impact of GDP, primary and renewable energy consumption, human development index and trade openness on methane emissions in OECD countries. Using advanced cointegration approaches, we find that GDP and primary energy consumption increase CH4 emissions, while renewable energy consumption and human development mitigate their growth. However, the impact of these variables varied over time. No significant effect of trade openness on methane emissions was found. We recommend specific policies for OECD countries to reduce methane emissions, especially for the most polluting countries. Governments should promote renewable energy sources (solar, wind, hydro) to reduce reliance on fossil fuels, thereby minimizing methane leakage during extraction and transport. In addition, investing in human development can promote sustainable behaviors and further reduce emissions, addressing both environmental and social concerns.

Active gas camera mass flow quantification (qOGI): Application in a biogas plant and comparison to state-of-the-art gas cams.

Gas cameras are primarily used to detect gas leaks, but their use has been increasingly extended to mass flow quantification (qOGI). We employ the previously published active illuminated gas camera [Bergau etal. "Real-time active-gas imaging of small gas leaks," J. Sens. Sens. Syst. 12, 61-68 (2023) and Bergau etal. "Flow rate quantification of small methane leaks using laser spectroscopy and deep learning," Process Saf. Environ. Prot. 182, 752-759 (2024)] in a real-world application for quantification, enhancing the camera with two new features: sensitivity adaptation and camera-gas distance detection. This technology was applied to a gas leak found in the pressure swing adsorption room of a biogas plant in Germany. We compare its performance with state-of-the-art quantification gas cameras (qOGI), such as Sensia Mileva 33. Such a comparison between active and passive gas cameras is possible for the first time due to the introduced sensitivity tuning. Additionally, we enclosed the gas leak and measure the methane concentration with a flame ionization detector, providing a gold standard for comparison. Our findings revealed relative offsets to our gold standard of -57% and +319% for the DAS-camera and the Sensia, respectively, suggesting that the accuracy of mass flow quantification could be improved through the use of active gas cameras.

Downstream natural gas composition across U.S. and Canada: implications for indoor methane leaks and hazardous air pollutant exposures

Previous research has shown that natural gas (NG) leaks from residential appliances are common, affecting greenhouse gas emission inventories and indoor air quality. To study these implications, we collected and analyzed 587 unburned NG samples from 481 residences over 17 North American cities for hydrocarbons, hazardous air pollutants, and organosulfur odorants. Nearly all (97% of) gas samples contained benzene (between-city mean: 2335 ppbv [95% CI: 2104, 2607]) with substantial variability between cities. Vancouver, Los Angeles, Calgary, and Denver had at least 2x higher mean benzene concentrations than other cities sampled, with Vancouver exhibiting a nearly 50x greater mean benzene level than the lowest-concentration city (Boston). We estimate that current U.S. and Canadian emissions inventories are missing an additional 25 000 [95% CI: 19 000, 34 000] and 4000 [95% CI: 3700, 5200] lbs benzene yr−1 through downstream NG leakage, respectively. Concentrations of odorants added for leak detection varied substantially across cities, indicating a lack of standardization. Houston, for instance, had 5x higher mean tert-butyl mercaptan levels than Toronto. Using these odorant measurements, we found that methane emissions as high as 0.0080–0.28 g h−1 and indoor benzene enhancements 0.0096–0.11 ppbv could go undetected by persons with an average sense of smell, with large uncertainties driven by smelling sensitivity, gas composition, and household conditions. We also observed larger leaks (>10 ppm ambient methane) in ∼4% of surveyed homes, confirming that indoor leakage occurs at varying degrees despite the presence of odorants. Overall, our results illustrate the importance of downstream NG composition to understand potential emissions, exposures, and odor-mediated leak detection levels. Given methane’s global warming potency, benzene’s toxicity, and wide variation in smelling abilities, our findings highlight the deficiencies regarding the sole reliance on odorization to alert and protect all occupants from indoor leaks.

Drone-Based Methane Leak Screening in Energy Infrastructure

Drone-Based Methane Leak Screening in Energy Infrastructure

A technique for detecting hydrogen and methane using refractive index sensitivity

Hydrogen and methane, as lightweight, high-energy fuels, occupy an important position in energy utilization and industrial production, and have broad application prospects. The safe extraction and production of new energy gases, as well as the safe utilization of hydrogen and methane is increasingly essential. The problem of detecting the type and concentration of hydrogen and methane is very important. This paper proposed a multi-peak high performance metamaterial refractive index sensor to fulfill the research gap for hydrogen or methane detection. We made unique designs on the patterns of the metasurface and made innovative combinations of materials. Through discussing different shapes and geometrical parameters, we get an optimal structure with a perfect absorption state, high sensitivity, and polarization independence. In the near-infrared spectral range spanning from 1700 nm to 2600 nm, resonance peaks were observed in the absorption spectrum at wavelengths of 1738.27 nm, 1843.17 nm, and 2368.13 nm. These peaks exhibited absorption rates respectively are 99.28 %, 89.71 %, and 99.69 %. The high sensitivity of the sensor under different environmental refractive indices was up to 715.43 nm/RIU. This leads to more precise and reliable identification of hydrogen and methane. The polarization dependence of our structure ensures consistent results under light illumination from various angles. This feature enhances the convenience of using it in both production and daily life, with fewer constraints and more accurate outcomes. The possible applications of this study lie in detecting the presence of hydrogen and methane gases, the exploration and extraction of new energy gases, as well as to monitoring and alarm systems for hydrogen and methane leaks. Moreover, it can serve as a validation system for the results of hydrogen and methane production processes. These applications are of significant importance for environmental protection and process safety.

Geochemical tracers associated with methane in aquifers overlying a coal seam gas reservoir

Understanding inter-aquifer connectivity or leakage of greenhouse gases and groundwater to aquifers overlying gas reservoirs is important for environmental protection and social licence to operate. Australia's Great Artesian Basin (GAB) is the largest artesian groundwater system in the world with groundwater extracted for agriculture, livestock, mines, energy, private or town water supply. Microbial coal seam gas (CSG) and production water are also extracted from the GAB. Here a range of groundwater tracers is used to investigate the potential for gas and groundwater connectivity between the CSG reservoir and aquifers.The GAB aquifer and alluvium contained a range of methane concentrations (0.001 to 2100 mg/L) that exhibit an increase with depth and δ13C-CH4. Aquifer and alluvium groundwater 87Sr/86Sr were in the range 0.7042 to 0.7082. CSG production waters however had non-radiogenic, distinctive 87Sr/86Sr signatures <0.7036, indicating a lack of significant groundwater leakage. One gassy aquifer bore with 160 mg/L methane conversely has 87Sr/86Sr, δ13C-CH4, δ2H-CH4 and δ13C-DIC values overlapping the CSG waters. In several aquifers δ34S-SO4 and δ18O-SO4 are sourced from windblown surface salts of inland Australian playa lakes in recharge waters. Bacterial sulphate reduction is additionally occurring in a regional aquifer. Cosmogenic isotopes and tritium show recent recharge and mixing with older groundwaters in several shallow aquifers.Groundwater and gas signatures indicate that leakage of groundwater and methane from the CSG reservoir was not occurring in the majority of areas investigated here. Methane was consistent with in situ generation in shallow GAB aquifers by primary microbial CO2 reduction or acetate fermentation. Connectivity of one alluvial bore and the underlying GAB aquifer could not be completely ruled out. Separately, one gassy Springbok GAB aquifer bore is either connected to the underlying CSG gas reservoir, or has in situ secondary microbial CO2 reduction producing methane from interbedded coal within the aquifer. This study is relevant to other basins in Australia and internationally where gas is observed in aquifers that overly conventional, unconventional or coal seam gas reservoirs.

Quantification of methane oxidation measuring isotopic signal in 13C on Spanish landfills

Landfill emissions, particularly methane leaks detected by satellite, are drawing great attention in the last years as a mean for evaluate their contribution to the global warming effect. In contrast, models like IPCC often overestimate landfill methane emissions, prompting verification and mitigation system evaluation. Methane's higher warming capacity than carbon dioxide underscores the importance of promoting its oxidation as it traverses landfill layers. This oxidation raises the CH4–13C/12C ratio via bacterial biooxidation. This study quantified this fractionation using soil and surface gas samples from Spanish landfills and their degassing systems. Sampling relied on walkover surveys collecting samples in Tedlar bags, to analyze isotopic signals in the laboratory using WS-CRDS. Fractionation factors (α) ranged from 1.020 to 1.030, while the oxidized fraction (fox) spanned from no oxidation to 55% (δ13C of −45.83‰). Each ratio correlates with emission types like fugitive and dispersed emissions on plateaus, berms, slopes, sealing cracks, or pits. Understanding the methane oxidized fraction in each landfill is relevant for greenhouse gas emission model integration.

Response of early diagenesis to methane leakage in the inner shelf of the East China Sea

Shelf seas are experiencing a rise in shallow gas leaks, primarily methane, raising concerns due to their environmental impact. However, the effect of the leaks on early diagenesis remains poorly understood. This study analyzes sediment lithology, organic geochemistry and porewater geochemistry of two short cores collected nearby the pockmarks in the muddy inner shelf of the East China Sea. Our findings clearly demonstrate the impact of methane leakage on early diagenesis, evidenced by the shallower position of the SMTZ (sulfate-methane transition zone), higher concentrations of uranium (U), vanadium (V), and manganese (Mn) in the porewater near and above the SMTZ, and downcore decrease in Mg2+, Ca2+, and Sr2+ concentrations versus increase in Mg2+/Ca2+ and Sr2+/Ca2+ ratios. Their profile variations and the difference between two cores are determined by the intensity of methane leakage. The estimated methane diffusive flux of 619 mmol m-2 yr-1 at YEC7–2 is roughly 8.5 times that at YEC7–1 (73 mmol m-2 yr-1), consistent with a shorter distance of YEC7–2 to the pockmark with active methane leakage. A schematic model is summarized to demonstrate the response of early diagenesis processes to the increasing methane leakages in response to changing sedimentation regimes from accretion to severe erosion. This study undoubtedly improves our understanding mutual promotion effect between seafloor erosion and gas leakage, and their impact on early diagenesis processes and resultant porewater geochemical changes and authigenic mineral records.

A methane monitoring station siting method based on WRF-STILT and genetic algorithm

Reducing methane emissions in the oil and gas industry is a top priority for the current international community in addressing climate change. Methane emissions from the energy sector exhibit strong temporal variability and ground monitoring networks can provide time-continuous measurements of methane concentrations, enabling the rapid detection of sudden methane leaks in the oil and gas industry. Therefore, identifying specific locations within oil fields to establish a cost-effective and reliable methane monitoring ground network is an urgent and significant task. In response to this challenge, this study proposes a technical workflow that, utilizing emission inventories, atmospheric transport models, and intelligent computing techniques, automatically determines the optimal locations for monitoring stations based on the input quantity of monitoring sites. This methodology can automatically and quantitatively assess the observational effectiveness of the monitoring network. The effectiveness of the proposed technical workflow is demonstrated using the Shengli Oilfield, the second-largest oil and gas extraction base in China, as a case study. We found that the Genetic Algorithm can help find the optimum locations effectively. Besides, the overall observation effectiveness grew from 1.7 to 5.6 when the number of site increased from 1 to 9. However, the growth decreased with the increasing site number. Such a technology can assist the oil and gas industry in better monitoring methane emissions resulting from oil and gas extraction.

On the cost of zero carbon electricity: A techno-economic analysis of combined cycle gas turbines with post-combustion CO2 capture

To achieve a sustainable electricity grid, affordable and dispatchable power capacity that supports grid stability and does not increase atmospheric CO2 levels will be required. Combined cycle gas turbines (CCGTs) with post-combustion CO2 capture (PCC) can meet these requirements by capturing and permanently storing all combustion CO2 emissions and, coupled with negative emissions technologies, any remaining life-cycle emissions. For the first time, we present a comprehensive analysis of the technical and financial challenges of producing zero-carbon electricity from CCGTs on a life-cycle basis. We conclude that when the design is optimised, fossil CO2 capture fractions can be increased from 96% to 100% with minimal process modification, commercially available technology and an additional 0.5% decrease in thermal efficiency. This represents a significant 60–70% reduction in the additional efficiency penalty required to reach zero CO2 emission operation. The Cost of CO2 Avoided of 100% fossil CO2 capture is just 128 £/tCO2, a 3 £/tCO2 increase over the 95% gross CO2 capture fraction required to permit PCC projects in the UK. Indeed, within the bounds of the UK power CCS business model, we show that 100% fossil CO2 capture maximises both variable and capacity payments to the producer, resulting in a 2% decrease in the cost of power produced. For zero-carbon electricity on a life-cycle basis, the recapture and permanent geological storage of all remaining life-cycle CO2e emissions from plant construction & decommissioning, CO2 T&S network operation and the natural gas supply chain (operational CO2e emissions and methane leakage) increases the median Cost of CO2 Avoided to 178 £/tCO2 (130–371 £/tCO2), leading to the novel conclusion that a market mechanism equating to a CO2 price of over 178£/tCO2 is likely sufficient to incentivise the development of truly CO2-neutral CCGTs.

Report on Landsat 8 and Sentinel-2B observations of the Nord Stream 2 pipeline methane leak

Abstract. In late September 2022, explosions of the Nord Stream pipelines caused what could be the largest anthropogenic methane leak ever recorded. We report on Landsat 8 (L8) and Sentinel-2B (S-2B) observations of the sea-foam patch produced by the Nord Stream 2 (NS2) leak located close to Bornholm island, acquired on 29 and 30 September, respectively. Usually, reflected sunlight over sea is insufficient for these Earth imagers to observe any methane signal in nadir-viewing geometry. However, the NS2 foam patch observed here is bright enough to possibly allow the detection of methane above it. We apply the multi-band single-pass (MBSP) method to infer methane enhancement above the NS2 foam patch and then use the integrated mass enhancement (IME) method in a Monte Carlo ensemble approach to estimate methane leak rates and their uncertainties. This very specific NS2 observation case challenges some of MBSP and IME implicit assumptions and thus calls for customized calibrations: (1) for MBSP, we perform an empirical calibration of sea-foam albedo spectral dependence by using sea-foam observations in ship trails, and (2) for IME, we yield a tailored effective wind speed calibration that accounts for a partial plume observation, as methane enhancement may only be seen above the NS2 sea-foam patch. Our comprehensive uncertainty analysis yields large methane leak rate uncertainty ranges that include zero for single overpasses and, assuming they are independent, a best estimate of 502 ± 464 t h−1 for the combined averaged L8 and S-2B emission rate. Within all our Monte Carlo ensembles, positive methane leak rates have higher probabilities (80 %–88 %) than negative ones (12 %–20 %), thus indicating that L8 and S-2B likely captured a methane-related signal. Overall, we see our work both as a nuanced analysis of L8 and S-2B contributions to quantifying the NS2 leak emissions and as a methodological cautionary tale that builds insight into MBSP and IME sensitivities.

Mitigating the Invasive Method of Hydraulic Fracturing Through a Phase Out Policy Plan

Hydraulic fracturing, or fracking, is a process used to extract natural gas from shale deposits deep below the surface. Fracking is heralded as a “clean” energy source compared to other extraction methods due to comparatively low carbon emissions. The fracking industry decreases the U.S.’s dependence on foreign nations for energy and brings valuable job opportunities when sites are first established; however, affected communities do not experience the benefits of these economic “booms” for long. Concerns like increased cancer risk from air and water contamination are linked to fracking activity. Fracking operators are not required to disclose the contents of ‘proprietary’ fracking fluids used in extraction, which are known to contain chemicals that threaten public and environmental health. Fracking has detrimental effects on national public health and contributes to climate change through elevated methane emissions. Therefore, to help mitigate these challenges, we recommend a phase out plan including 1) increasing setback requirements and eliminating any exemptions, 2) managing methane (CH₄) leakages and improving monitoring systems on all sites, 3) mandating disclosure reports, and 4) mandating the collection of preliminary data to facilitate a bottom-up approach to management. We use Pennsylvania as a case study due to the state’s prevalence of fracking and the current policies and regulations in place for drilling.

Glacial-interglacial sedimentation control on gas seepage exemplified by Vestnesa Ridge off NW Svalbard margin

Vestnesa Ridge is built-up of thick contourites mainly deposited during the last ∼5 million years. Methane leaks from deep gas reservoirs creating pockmarks on its crest, and which have been the focus of numerous studies. Sedimentation patterns in relation to the pronounced changes in oceanography and climate of the last glacial-interglacial cycles and its possible impact of seepage of gas have rarely been studied. Here, we present a detailed history of contourite development covering the last ∼130,000 years with most details for the last 60,000 years. The study is based on 43 marine sediment cores and 1,430 km of shallow seismic lines covering the ridge including methane seep sites, with the purpose of reconstructing changes in depositional patterns in relation to paleoceanographical changes on glacial, interglacial, and millennial time scale in relation to activity of seepage of gas. The results show that thick Holocene deposits occurred below ∼1,250 m water depth in the western part of the ridge. Both in pockmarks at western and eastern Vestnesa Ridge, seepage decreased at ∼10–9 ka in the early Holocene. The fine Holocene mud likely reduced seepage to a slow diffusion of gas and microbial oxidation probably prevented escape from the seafloor. Results also showed that seepage of gas was highly variable during the glacial, and low to moderate during the cold Heinrich stadial H1 (19–15 ka) and Younger Dryas stadial (13–12 ka). Seepage reached a maximum during the deglaciation in the Bølling and Allerød interstadials 15–13 ka and early Holocene 12–10 ka. The deglaciation was a period of rapid climatic, oceanographic, and environmental changes. Seepage of gas varied closely with these events indicating that slower tectonic/isostatic movements probably played a minor role in these millennial scale rapid fluctuations in gas emission.

Sensor Data Analytics for Optimized Methane Leak Detection and Mitigation

Sensor Data Analytics for Optimized Methane Leak Detection and Mitigation

CLIMATE CHANGE MITIGATION STRATEGIES IN THE OIL &amp; GAS SECTOR: A REVIEW OF PRACTICES AND IMPACT

Climate change mitigation has become a pressing global challenge, with the oil and gas sector being a significant contributor to greenhouse gas emissions. This review examines climate change mitigation strategies within the oil and gas industry, focusing on practices and their impact. The oil and gas industry faces increasing pressure to reduce its carbon footprint and transition towards cleaner energy sources. Various mitigation strategies have been implemented, including technological innovations, operational improvements, and investments in renewable energy. These strategies aim to minimize greenhouse gas emissions, improve energy efficiency, and transition towards low-carbon alternatives. Technological innovations play a crucial role in mitigating climate change within the oil and gas sector. Advanced drilling techniques, such as horizontal drilling and hydraulic fracturing, have enabled companies to extract oil and gas more efficiently, reducing emissions per unit of production. Additionally, carbon capture, utilization, and storage (CCUS) technologies have been developed to capture and store carbon dioxide emissions from oil and gas operations, preventing them from entering the atmosphere. Operational improvements, such as reducing methane leaks and flaring, are also essential for climate change mitigation in the oil and gas industry. Methane is a potent greenhouse gas, and minimizing its release during extraction, processing, and transportation is critical for reducing the sector's overall emissions. Companies have implemented measures such as leak detection and repair programs, improved equipment maintenance, and enhanced monitoring systems to mitigate methane emissions effectively. Furthermore, investments in renewable energy and low-carbon technologies are increasingly common among oil and gas companies. Many companies are diversifying their portfolios to include solar, wind, and bioenergy projects, aiming to reduce their reliance on fossil fuels and contribute to the transition to a low-carbon economy. In conclusion, climate change mitigation strategies in the oil and gas sector encompass a range of technological, operational, and investment initiatives aimed at reducing greenhouse gas emissions and transitioning towards cleaner energy sources. While progress has been made, ongoing efforts and collaboration between industry stakeholders, governments, and civil society are essential to achieve meaningful impact in mitigating climate change.&#x0D; Keywords: Climate Change, Mitigation, Strategies, Oil and Gas Sector, Practices and Impact.

An environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting

During the pivotal period of energy transition between carbon neutrality and carbon peaking, it is crucial to develop the natural gas hydrate (NGH) due to the advantages of high energy density and non-pollution. However, the NGH production also faces several significant environmental challenges that need to be addressed such as seawater intrusion, methane leakage, and submarine landslides. Therefore, an environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting was introduced. As a novel method for achieving the two goals of both reservoir skeleton reinforcement and permeability enhancement, is proposed to stimulate NGH reservoir. Herein, the formulation based on foamed ultrafine cement-based grout was established. The results showed that the grout has good fluidity with initial viscosity ∼500 mPa·s and consolidation time in the range of 28–50 min. Meanwhile, the consolidation performance evaluation was studied, and it showed that the consolidation is with porosity in the range of 9.41%–46.59%, permeability in the range of 51.23 mD-789.07 mD, and compressive strength in the range of 3.31 MPa–3.88 MPa. The internal pore channels are uniformly distributed with a large number of stomatal strings, which can be used as a multistage seepage channel for gas and water production from hydrate decomposition. To further examine the stimulating behavior, the effect of hydrate saturation, grouting well diameter, grouting flow rate, and in-situ stress on splitting pressure and grouting volume were analyzed, and it was found that the grout has good ability to split fracturing and grout diffusion under the conditions of axial pressure of 5 MPa, confining pressure of 4 MPa, and hydrate saturation not more than 0.30. In addition, an environmental-benign high-efficient reservoir stimulation method on a laboratory scale was proposed. The findings could provide fundamental insights and recommendations for the implementation of splitting grouting in NGH reservoirs.

City-scale methane emissions from the midstream oil and gas industry: A satellite survey of the Zhoushan archipelago

As the second most abundant greenhouse gas after carbon dioxide, methane (CH4) leakage and emissions pose potential climate threats and environmental problems in the midstream oil and gas storage and transportation (OGST) industry. In this study, the Tropospheric Monitoring Instrument on the Sentinel-5P satellite was adopted to investigate the coverage of atmospheric CH4 concentrations over the Zhoushan archipelago, which is China's largest OGST base. Specifically, the distribution of atmospheric CH4 and nitrogen dioxide (NO2) concentrations over Zhoushan in August 2022 and August 2023 were evaluated, where changes in concentrations around the OGST companies were monitored. Using surface temperature inversion and average temperature statistics, we analyzed the heat island effect in Zhoushan. The results showed that: (1) although there is limited valid data (>200 pixel/day) for Zhoushan, the amount of valid data increased from 3.2% in January 2020 to 32.3% in August 2023; (2) around the region of the OGST companies, the atmospheric CH4 concentration shown significant variation at both the spatial and temporal scales, which may be due to the storage, loading, and unloading of petroleum products; (3) under geographic isolation conditions, NO2 can be used as a tracer gas to track the CH4 emissions from OGST companies; and (4) Surface temperature analysis underscores OGST companies' contribution to Zhoushan's urban heat island effect, with local average temperature increases outstripping broader national trends, highlighting the intricate interplay of human and natural factors in the city-scale climate dynamics.

Simulation evaluation of a single-photon laser methane remote sensor for leakage rate monitoring.

We propose a novel methane leakage rate remote sensor that combines a single-photon avalanche diode detector with a near-infrared 1653.7 nm low-power laser. The proposed M sequence and triangle wave signal modulation method simultaneously realizes the detection of methane leakage and target point clouds. Innovatively, the sensor's methane concentration and leakage rate quantification ability were simulated by combining the Gaussian plume diffusion model and the Risley prism. The effects of the prism rotation ratio, wind speed, leakage rate, atmospheric stability (AS), target reflectivity, signal averaging period, and concentration spatial interpolation method on leakage rate are discussed. When plume methane concentrations reduce from 10,000 to 500 ppm·m, the relative concentration bias rise from 1% to 30%, the absolute concentration bias is approximately 100 ppm·m. Two spatial concentration interpolation methods introduced leakage rate bias ranging from 6%-25%. For a low AS, the leakage rate bias under the cubic interpolation method was small (approximately 1.6%). In addition, when the initial leakage rate increased from 100 to 1,000 mg/s, the leakage rate bias was approximately 20% smaller.

Monitoring underwater volcano degassing using fiber-optic sensing

Continuous monitoring of volcanic gas emissions is crucial for understanding volcanic activity and potential eruptions. However, emissions of volcanic gases underwater are infrequently studied or quantified. This study explores the potential of Distributed Acoustic Sensing (DAS) technology to monitor underwater volcanic degassing. DAS converts fiber-optic cables into high-resolution vibration recording arrays, providing measurements at unprecedented spatio-temporal resolution. We conducted an experiment at Laacher See volcano in Germany, immersing a fiber-optic cable in the lake and interrogating it with a DAS system. We detected and analyzed numerous acoustic signals that we associated with bubble emissions in different lake areas. Three types of text-book bubbles exhibiting characteristic waveforms are all found from our detections, indicating different nucleation processes and bubble sizes. Using clustering algorithms, we classified bubble events into four distinct clusters based on their temporal and spectral characteristics. The temporal distribution of the events provided insights into the evolution of gas seepage patterns. This technology has the potential to revolutionize underwater degassing monitoring and provide valuable information for studying volcanic processes and estimating gas emissions. Furthermore, DAS can be applied to other applications, such as monitoring underwater carbon capture and storage operations or methane leaks associated with climate change.