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\"This book uses actual construction projects as examples to elaborate the various technologies regarding groundwater control and airtightness guarantees for the construction of large storage rock caverns in complicated geological conditions. It introduces the latest technologies to give hands-on experience on what to do in unexpected geological conditions, and provides insight into the design, construction and operation of underground facilities. The book is hence useful in feasibility studies, developments, and other research into these underground facilities. Drawing on the experience gained from building Japan's largest LPG storage caves, Storage of LPG in Large Rock Caverns is a must-read for engineers, academics and students in the fields of rock mechanics, geotechnical engineering and related disciplines\"-- Provided by publisher.

Underground hydrogen storage is a long‐duration energy storage option for a low‐carbon economy. Although research into the technical feasibility of underground hydrogen storage is ongoing, existing underground gas storage (UGS) facilities are appealing candidates for the technology because of their ability to store and deliver natural gas. We estimate that UGS facilities in the United States (U.S.) can store 327 TWh (9.8 MMT) of pure hydrogen. A complete transition to hydrogen storage would reduce the collective working‐gas energy of UGS facilities by ∼75%; however, most (73.2%) UGS facilities could maintain current energy demand using a 20% hydrogen‐natural gas blend. U.S. UGS facilities can buffer 23.9%–44.6% of the high and low hydrogen demand projected for 2050, respectively, which exceeds the current percentage of natural gas demand buffered by storage. Thus, transitioning UGS infrastructure to hydrogen could substantially reduce the number of new hydrogen storage facilities needed to support a hydrogen economy. Plain Language Summary Hydrogen is a high energy content fuel that can be produced with low or zero greenhouse gas emissions from water and other chemicals. Creating hydrogen during periods of energy surplus and storing it underground is one long‐duration, low‐emission, energy storage option that can balance supply and demand for an entire electric grid. In the United States (U.S.), existing underground gas storage (UGS) facilities are a logical first place to consider subsurface hydrogen storage, because their geology has proven favorable for storing natural gas. We estimated that existing UGS facilities can store 327 TW‐h (9.8 million metric tons) of pure hydrogen. Transitioning from natural gas to pure hydrogen storage would reduce the total energy stored in existing UGS facilities by ∼75%. Storing hydrogen‐natural gas mixtures also reduces energy storage potential, but most (73.2%) UGS facilities can meet current energy demands with a 20% hydrogen blend. U.S. UGS facilities can store 23.9%–44.6% of the projected high and low hydrogen demand for 2050, respectively, suggesting that a partial transition of UGS infrastructure could reduce the need for new hydrogen storage facilities. These findings motivate research that explores the technical feasibility of underground hydrogen storage in natural gas storage reservoirs. Key Points The total hydrogen working‐gas energy of underground gas storage facilities in the United States is estimated to be 327 TW‐hours Most (73.2%) underground gas storage facilities can store hydrogen blends up to 20% and continue to meet their current energy demand Hydrogen storage in existing underground gas storage facilities can sufficiently buffer the hydrogen demand projected for 2050

We present a multiscale seismic attenuation tomography of a seismotectonically complex region in northern Italy hosting the well‐characterized Collalto Underground Gas Storage (UGS). Beyond its specific relevance, this site provides a natural laboratory for assessing the ability of attenuation imaging to distinguish fluid‐rich zones from highly strained, failure‐prone volumes. We integrated scattering and absorption tomography models: scattering anomalies, between the two principal thrusts, highlight localized strain near fault tips; absorption tomography images the shallow UGS and reveals a deeper fluid‐saturated volume. Seismicity concentrated around this deeper anomaly, exhibiting a pulsatory temporal pattern, suggests a fluid‐driven role in the deformation processes. These findings show that attenuation tomography, combined with multiscale and complementary geophysical models, can resolve critical subsurface features related to fluids and strain. The approach is broadly applicable to geothermal and volcanic contexts and supports seismic hazard assessment in tectonically active regions where natural and anthropogenic processes may interact.

Coupling of power-to-gas processes with underground gas storage could effectively allow surplus electricity to be stored for later use. Depleted hydrocarbon reservoirs could be used as stores, but practical experience of hydrogen storage in such sites is limited. Here we present data from a field trial that stored 119,353 m 3 of hydrogen admixed to natural gas in a depleted hydrocarbon reservoir. After 285 days, hydrogen recovery was 84.3%, indicating the process’s technical feasibility. Additionally, we report that microbes mediated hydrogen conversion to methane. In laboratory experiments studying mesocosms that mimic real reservoirs, hydrogen and carbon dioxide were converted to methane (0.26 mmol l −1  h −1 evolution rate) reproducibly over 14 cycles in 357 days. This rate theoretically allows 114,648 m 3 of methane per year to be produced in the test reservoir (equivalent to ~1.08 GWh). Our research demonstrates the efficiency of hydrogen storage and the importance of geo-methanation in depleted hydrocarbon reservoirs. Geologic formations could be used for hydrogen storage and conversion to methane, yet technical feasibility is unclear as field-scale data are lacking. Here the authors perform field tests demonstrating that hydrogen can be stored and microbially converted to methane in a depleted underground hydrocarbon reservoir.

The existing infrastructure of the natural gas transportation pipeline network and underground gas storage (UGS) facilities in Germany provides an opportunity and huge capacity to feed, transport and store hydrogen and synthetic fuel gases containing hydrogen, produced from renewable sources. At low hydrogen concentrations, only minor changes to gas transportation equipment will be required. In contrast, the UGS designed in converted gas fields and aquifers are particularly susceptible to the effect of hydrogen. Due to a lack of adequate knowledge about the hydrogen concentration in natural gas, which can be tolerated by the downhole equipment, reservoir and caprocks, the injection of natural gas containing hydrogen in the existing porous UGS is strongly limited. Key issues addressed in this paper are the change in capacity and efficiency of UGS associated with the blending of hydrogen in the stored natural gas, the geological integrity of the reservoir and caprocks, the technical integrity of gas storage wells, durability of the materials used for well completions, corrosion and environmental risks associated with the products of microbial metabolism.

Accurate and timely detection, quantification, and attribution of methane emissions from Underground Gas Storage (UGS) facilities is essential for improving confidence in greenhouse gas inventories, enabling emission mitigation by facility operators, and supporting efforts to assess facility integrity and safety. We conducted multiple airborne surveys of the 12 active UGS facilities in California between January 2016 and November 2017 using advanced remote sensing and in situ observations of near-surface atmospheric methane (CH4). These measurements where combined with wind data to derive spatially and temporally resolved methane emission estimates for California UGS facilities and key components with spatial resolutions as small as 1-3 m and revisit intervals ranging from minutes to months. The study spanned normal operations, malfunctions, and maintenance activity from multiple facilities including the active phase of the Aliso Canyon blowout incident in 2016 and subsequent return to injection operations in summer 2017. We estimate that the net annual methane emissions from the UGS sector in California averaged between 11.0 3.8 GgCH4 yr−1 (remote sensing) and 12.3 3.8 GgCH4 yr−1 (in situ). Net annual methane emissions for the 7 facilities that reported emissions in 2016 were estimated between 9.0 3.2 GgCH4 yr−1 (remote sensing) and 9.5 3.2 GgCH4 yr−1 (in situ), in both cases around 5 times higher than reported. The majority of methane emissions from UGS facilities in this study are likely dominated by anomalous activity: higher than expected compressor loss and leaking bypass isolation valves. Significant variability was observed at different time-scales: daily compressor duty-cycles and infrequent but large emissions from compressor station blow-downs. This observed variability made comparison of remote sensing and in situ observations challenging given measurements were derived largely at different times, however, improved agreement occurred when comparing simultaneous measurements. Temporal variability in emissions remains one of the most challenging aspects of UGS emissions quantification, underscoring the need for more systematic and persistent methane monitoring.

This study investigates ground deformations in the southeastern Po Plain (northern Italy), focusing on the Bologna area—a densely populated region affected by natural and anthropogenic subsidence. Ground deformations in the area result from geological processes (e.g., sediment compaction and tectonic activity) and human activities (e.g., ground water production and underground gas storage—UGS). We apply a multidisciplinary approach integrating subsurface geology, ground water production, advanced differential interferometry synthetic aperture radar—DInSAR, gas storage data, and land use information to characterize and analyze the spatial and temporal variations in vertical ground deformations. Seasonal and trend decomposition using loess (STL) and cluster analysis techniques are applied to historical DInSAR vertical time series, targeting three representatives areas close to the city of Bologna. The main contribution of the study is the attempt to correlate the lateral extension of ground water bodies with seasonal ground deformations and water production data; the results are validated via knowledge of the geological characteristics of the uppermost part of the Po Plain area. Distinct seasonal patterns are identified and correlated with ground water production withdrawal and UGS operations. The results highlight the influence of superficial aquifer characteristics—particularly the geometry, lateral extent, and hydraulic properties of sedimentary bodies—on the ground movements behavior. This case study outlines an effective multidisciplinary approach for subsidence characterization providing critical insights for risk assessment and mitigation strategies, relevant for the future development of CO2 and hydrogen storage in depleted reservoirs and saline aquifers.

The 2013 seismic sequence at the Castor injection platform offshore Spain, including three earthquakes of magnitude 4.1, occurred during the initial filling of a planned Underground Gas Storage facility. The Castor sequence is one of the most important cases of induced seismicity in Europe and a rare example of seismicity induced by gas injection into a depleted oil field. Here we use advanced seismological techniques applied to an enhanced waveform dataset, to resolve the geometry of the faults, develop a greatly enlarged seismicity catalog and record details of the rupture kinematics. The sequence occurred by progressive fault failure and unlocking, with seismicity initially migrating away from the injection points, triggered by pore pressure diffusion, and then back again, breaking larger asperities loaded to higher stress and producing the largest earthquakes. Seismicity occurred almost exclusively on a secondary fault, located below the reservoir, dipping opposite from the reservoir bounding fault. The 2013 Castor seismic sequence, offshore Spain, is a rare example of seismicity induced by gas storage operations. Here we show that early seismicity marked the progressive failure of a fault in response to pore pressure diffusion, while later larger earthquakes resulted by the failure of loaded asperities.

Underground gas storage (UGS) in depleted hydrocarbon reservoirs is a strategic practice to cope with the growing energy demand and occurs in many places in Europe and North America. In response to summer gas injection and winter gas withdrawal the reservoir expands and contracts essentially elastically as a major consequence of the fluid (gas and water) pore pressure fluctuations. Depending on a number of factors, including the reservoir burial depth, the difference between the largest and the smallest gas pore pressure, and the geomechanical properties of the injected formation and the overburden, the porous medium overlying the reservoir is subject to three‐dimensional deformation with the related cyclic motion of the land surface being both vertical and horizontal. We present a methodology to evaluate the environmental impact of underground gas storage and sequestration from the geomechanical perspective, particularly in relation to the ground surface displacements. Long‐term records of injected and removed gas volume and fluid pore pressure in the “Lombardia” gas field, northern Italy, are available together with multiyear detection of vertical and horizontal west‐east displacement of the land surface above the reservoir by an advanced permanent scatterer interferometric synthetic aperture radar (PSInSAR) analysis. These data have been used to calibrate a 3‐D fluid‐dynamic model and develop a 3‐D transversally isotropic geomechanical model. The latter has been successfully implemented and used to reproduce the vertical and horizontal cyclic displacements, on the range of 8–10 mm and 6–8 mm, respectively, measured between 2003 and 2007 above the reservoir where a UGS program has been underway by Stogit‐Eni S.p.A. since 1986 following a 5 year field production life. Because of the great economical interest to increase the working gas volume as much as possible, the model addresses two UGS scenarios where the gas pore overpressure is pushed from the current 103%pi, where pi is the gas pore pressure prior to the field development, to 107%pi and 120%pi. Results of both scenarios show that there is a negligible impact on the ground surface, with deformation gradients that remain well below the most restrictive admissible limits for the civil structures and infrastructures. Key Points Evaluation of the environmental impact of UGS projects Set‐up and calibration of a 3‐D FE transversally isotropic geomechanical model PSInSAR analysis to measure vertical/horizontal movements of the land surface

Natural gas storage is an effective solution to address the energy supply–demand imbalance, and underground gas storage (UGS) is a primary method for storing natural gas. The overarching goal of this study is to monitor and analyze surface deformation at the Hutubi underground gas storage facility in Xinjiang, China, which is the largest gas storage facility in the country. This research aims to ensure the stable and efficient operation of the facility through long-term monitoring, using remote sensing data and advanced modeling techniques. The study employs the SBAS-InSAR method, leveraging Synthetic Aperture Radar (SAR) data from the TerraSAR and Sentinel-1 sensors to observe displacement time series from 2013 to 2024. The data is processed through wavelet transformation for denoising, followed by the application of a Gray Wolf Optimization (GWO) algorithm combined with Variational Mode Decomposition (VMD) to decompose both surface deformation and gas pressure data. The key focus is the development of a high-precision predictive model using a Gated Recurrent Unit (GRU) network, referred to as GWO-VMD-GRU, to accurately predict surface deformation. The results show periodic surface uplift and subsidence at the facility, with a notable net uplift. During the period from August 2013 to March 2015, the maximum uplift rate was 6 mm/year, while from January 2015 to December 2024, it increased to 12 mm/year. The surface deformation correlates with gas injection and extraction periods, indicating periodic variations. The accuracy of the InSAR-derived displacement data is validated through high-precision GNSS data. The GWO-VMD-GRU model demonstrates strong predictive performance with a coefficient of determination (R[sup.2]) greater than 0.98 for the gas well test points. This study provides a valuable reference for the future safe operation and management of underground gas storage facilities, demonstrating significant contributions to both scientific understanding and practical applications in underground gas storage management.