Underground Facilities Research Articles

Verification of correction factors for determining mean annual levels of radon in underground facilities

The first verification of a tool developed to improve the work of controlling bodies, managers and employees of underground facilities subject to radiation protection requirements was conducted. The recommended values of correction factors were verified using archival results of measurements conducted for the Institute of Occupational Medicine in Łódź in seven underground workplaces in Poland over exposure periods of a month (10,8678 data) and a quarter of a year (53,688 data). In a cave two groups of monthly factors, produced estimates with almost 70% to 99% consistency with the measured values. Along tourist routes located in mines, a similar fit was obtained using three groups of correction factors for measurement results from March, June and July. In the extraction areas of active underground mines, the best fit was produced by factors calculated as averages for spaces varying in the degree of insulation and ventilation method, while in other departments of mining plants, by correction factors recommended for facilities equipped with mechanical ventilation systems. All the quarterly correction factors produced the best fit between estimated mean annual concentrations and measurement results obtained in the second quarter of the calendar year. A wide variation in result consistency (from 20–30 to 65–80%) obtained for two underground tourist routes in the fourth quarter of the year demonstrates that it is best not to adopt results from this measurement period (October-December) for estimating mean annual radon concentration using the set of quarterly correction factors.

Screening the quality of legal and illegal dietary supplements by LC-MS/MS

ABSTRACT Dietary supplements are widely consumed. However, the lack of mandatory testing results in limited data on their quality, particularly in Eastern Europe. In this study, 21 legally registered and 9 illegal supplements, seized from an underground facility by the Polish Police, were examined. Contaminants were screened by utilising high-performance liquid chromatography coupled with untargeted mass spectrometry. The analysis identified 32 contaminants in the 30 dietary supplements examined. Untargeted analysis revealed a concerning issue: the intentional adulteration of both legal and illegal supplements with pharmacologically active substances that are prohibited in this category of products. This study indicated that many dietary supplements are of low quality due to deliberate adulteration or inadequate manufacturing conditions. The presence of unregistered or unapproved substances in these supplements poses serious health risks. Strong legal regulations are essential to address this issue effectively.

Geometrization of a 3D numerical model of an underground facility based on the results of terrestrial laser scanning

Abstract The article proposes a method of combining CloudCompare, RHINO, and FLAC3D software, aimed at building numerical models of underground objects of natural or engineering origin, based on the results of measurements made using terrestrial laser scanning technology. This technology is one of the most advanced in mine survey as it enables accurate mapping of even the most complex geometries of underground facilities. This opens wide possibilities in the construction of more accurate numerical models of the behavior of the rock mass around such underground objects. The results of simulation of the behavior of the rock mass around the analyzed excavations, obtained by performing numerical calculations, allow predicting unfavorable phenomena that may occur as a result of the destruction of the rock mass and which may threaten the safety of users of underground facilities, for example, caves, tunnels, and mining excavations. In this work, we carried out measurements using a terrestrial laser scanner and obtained a “point cloud” that reproduced the geometry of the underground facility. An example is a fragment of the adit St. Johannes, which is part of the underground tourist route “Geopark” St. Johannes Mine in Krobica in Lower Silesia in Poland in the neighborhood of Gierczyn and Przecznica. In the next step, the measurement results were processed, so that it was possible to import the generated geometry into the FLAC3D software and use it to build a numerical model of the adit, based on “brick” zones. The aim of the article is to present in detail the methodology of geometrization of numerical models of underground objects with complex geometry. The author wanted the method to be as easy to use as possible, give full control over the surface structure, and not require many numerical modeling programs.

Optimization of spatial layouts for underground facilities to achieve carbon neutrality in cities: A multi-agent system model

Subways, underground logistics systems and underground parking, as the primary facilities types of underground, contribute significantly to the achievement of carbon–neutral cities by moving surface transportation to underground, thereby releasing surface space for the creation of more urban blue-green space for carbon sink. Therefore, in-depth studies on carbon neutrality strategies as well as reliable layout optimization solutions of these three types of underground facilities are required. This study proposes a spatial layout optimization strategy for carbon neutrality using underground hydrogen storage and geothermal energy for these three types of underground facilities employing a multi-agent system model. First, three spatial layout relationships, competition, coordination, and followership, between five underground facilities that contribute to emission reduction were investigated. Second, the implementation steps for optimizing the spatial layout of underground facilities were determined by defining the behavioral guidelines for spatial environment, underground facility, and synergistic agent. Finally, using the Tianfu New District in Chengdu City, China, as a case study, layouts of underground facilities under three different underground space development scenarios were simulated to verify the model. The findings of this study address the gap in the research on underground spatial facilities and their layout optimization in response to emission reduction. This study provided a significant reference for the study of underground space and underground resources at the planning level to aid in achieving carbon–neutral cities.

Acoustic emission monitoring for engineered barriers in nuclear waste disposal

To safely dispose of nuclear waste in underground facilities, engineered barrier systems are needed to seal shafts and galleries. The material used in these barriers must be adapted to the host rock parameters. Shrinking and cracking must be avoided to provide a barrier with almost zero permeability. For repositories in salt rock environments, several types of salt concrete (SC) are used. Within the project SealWasteSafe, we compared the performance of an innovative alkali-activated material (AAM) with standard SC in their hydration and hardening phase. To monitor the microstructural changes within the two materials SC and AAM, acoustic emission (AE) signals have been recorded for up to ~250 days on 340-liter-cubic specimens. The phenomenon of AE is defined as the emission of elastic waves in materials due to the release of localized internal energy. Such energy release can be caused by the nucleation of micro-fracture, e.g. in concrete while curing or when exposed to load. The occurrence of AE events gives first rough indications of microstructural changes and potentially occurring cracking and thus, provides insights for structural health monitoring (SHM). The results show, that for the first 28 days after casting, less AE activity was detected in the AAM compared to SC. After 61 days, in the AAM material, the number of AE events exceeded those observed in the SC. However, the majority of the AE detected in AAM was related to surface effects, and not to microstructural changes within the matrix. Additionally, the source location analysis indicated, that despite lower activity in SC, we observed some clustering of the events. In contrast, in AAM, the activity inside the specimen is randomly distributed over the whole volume. The monitoring results help to estimate the material’s sealing properties which are crucial to assess their applicability as sealing material for engineered barriers.

MECHANISED COAL EXPLOITATION IN THE "BREZJE" PIT OF THE "DJURDJEVIK" BROWN COAL MINE

In addition to the coal and electricity market and changing geopolitical circumstances, there are other sufficiently rational reasons for opening new underground mining facilities and modernizing existing mining methods.Significant limiting factors and influences, in complex mining-geological conditions, most significantly affect the possibilities of the mechanized way of mining brown coal. The "Brezje" pit is a part of the deposit where the mining-geological factors are complex and determined by the natural conditions of the deposit's genesis. Excavation methods and technologies in complex deposit conditions must be based on great flexibility and adaptability.The complexity of the tectonic structure in the "Đurđevik" pit justified the application of chamber excavation methods with borehole blasting, in various technical modifications and solutions. In all previous solutions, the degree of mechanization of the method was not significantly improved and all modifications of the chamber method were non-mechanized or semi- mechanized with a large participation of manual work, technology based on drilling and blasting, high risk of injuries, low utilization of deposits, unjustified economic effects of work. The aim of this paper is to give an adequate answer to the hypothesis "in the block structure of the deposit with pronounced tectonics, it is possible to reduce the unfavorable influence of the complex mining-geological factors of the deposit on the excavation method by choosing modern mechanization for underground exploitation". The mechanized chamber method of excavation is a conceptual solution for the possible application in complex conditions of the proposed flexible mechanization for work in the "Brezje" pit. The advantage of modern multifunctional mining machines is a high degree of adaptability to the elements of the coal layer with the use of different working mechanisms (tools) that can be changed in a very short time depending on the working phase of the process. Key words: Pit, complexity, factors, chamber method, flexible, multifunctional machine

Enhancing smoke management in underground parking areas using jet fan systems with a focus on dead-end areas

This study delves into the utilization of jet fans in underground parking structures for smoke management during fires, with a specific focus on enhancing smoke control near critical areas adjacent to dead-end sections through innovative jet fan designs. Through the analysis of airflow patterns and computational fluid dynamic simulations, the research aims to effectively contain smoke and prevent its dispersion to unaffected zones. Findings underscore the significance of parking layout designs in ventilation strategies and soot dispersion rates. Altering the downward orientation of the jet fan outlet results in a notable portion of smoke being confined within the parking facility. Additionally, widening the jet fan outlet, as proposed in the design, can enhance smoke evacuation in all directions. Two hazard detection scenarios were executed within the parking structure following the British standard (BS), with one scenario simulated as a fire ignition source. The chosen scenario considers all escape routes and evacuation procedures within the underground parking area based on architectural specifications. By employing OpenFOAM software with the buoyantBoussinesqPimpleFOAM solver, the study assesses the efficacy of this approach, achieving a reduction in airflow irregularities of over 30%. It also provides valuable insights for designers to refine their comprehension of jet fan design, recommending tailored designs for specific zones. This research offers practical guidance for designers to optimize jet fan configurations for effective smoke control in underground parking facilities.

아파트 매매가격 결정 요인에 관한 연구

Recent increases in apartment prices in Seoul have led to increased research on factors influencing apartment prices. This study focused on Mapo-gu, and the findings are as follows: Factors positively affecting apartment prices include total number of households, number of floors in the building, distance to middle schools, and distance to the Dangin-ri thermal power plant. Factors negatively affecting apartment prices include floor area, contract duration, distance to Mapo Resource Recovery Facility, and elapsed duration. Of particular note in this study is that the distance to the Dangin-ri thermal power plant does not influence apartment prices. As the distance to the Dangin-ri thermal power plant decreases, positive effects are observed. Factors such as the absence of fuel storage, underground facilities for major facilities, and park development on the site seem to be at play. This contrasts with the previous trend where operational thermal power plants were considered factors negatively affecting apartment investment decisions.Such findings could contribute to further analysis of investment decision factors for apartments in Mapo-gu in the future.

Ensuring the stability of deep boilers of high-rise buildings

In today's conditions, the development of underground space can rightly be considered one of the most important and dynamic directions in civil and industrial construction at the worldlevel. In Ukraine, underground construction is important in connection with Russia's aggressive war. Underground and buried structures are most actively built in large cities and megacities. The main reasons for the need to use underground space in cities include the lack of free territories within historically formed buildings and requirements for urban infrastructure development. Today, the underground space is used not onlyfor the placement of engineering communicationsand transport facilities, but also for the construction of public complexes, multi-story underground garages and parking lots, shopping centers, as well asburied parts of residential and office buildings. Structural solutions for underground and buried structures, as well as their construction methods, depend on spatial planning solutions, purpose, depth of laying, engineering-geological, climatic and seismic construction conditions, surface loads, and the proximity of other buildings and buildings. Today, the maximum depth of pits designed inurban conditions usually do not exceed 25-30 m, and the number of underground floors is five to six. Given the growing demand for underground space, especially in densely populated areas, designers and engineers face a number of challengesthat require innovative approaches and modern technologies. This includes the use of the latest methods of geotechnical modeling, the use of highquality materials that ensure the durability and safety of structures, and the implementation of effective water drainage and waterproofing systems. Particular attention should be paid to safety issues during the construction and operation of underground structures, as they may be exposed to natural and man-made factors, such as groundwater, soil movement, and seismic activity. An important aspect is also the provision of comfortable conditions for people using underground facilities, which includes ventilation, lighting and evacuation routes. Scientific research and the experience of international projects demonstrate that the correct use of underground space can significantly increase the efficiency of the use of urban areas, contribute to the steady development of cities and improve the quality of life of their residents. Investments in underground construction are becoming more and more justified in view of the long-term benefits and theneed to adapt to the conditions of the modern urban environment. In general, underground construction is an important direction that has significant potential for development and improvement in the future, responding to the challenges of time and contributing to the development of modern infrastructure.

Research on the Application of Efficient Replacement Technology for Wellhead Casing Heads in Gas Storage Facilities

When it comes to gas storage facilities, it generally refers to underground gas storage facilities. Underground gas storage is a supporting project of long-distance pipelines, which is an artificial gas field or reservoir formed by injecting natural gas back into the underground space where gas can be stored. Suqiao Gas Storage is currently the deepest buried and highest pressure storage group in China. The storage group is located in Bazhou City and Yongqing County, Hebei Province, consisting of 5 gas storage facilities including Su 1, Su 20, Su 4, Su 49, and Gu Xinzhuang. The designed storage capacity is 6.738 billion cubic meters, with a working gas of 2.332 billion cubic meters. As of the end of 2020, a total of 3.5 billion cubic meters of gas injection and 2 billion cubic meters of gas production have gradually played an important role in natural gas peak shaving and supply guarantee in the Beijing Tianjin Hebei region. The Su 49 well is an injection production well for the reuse of an old well in the Su 49 gas storage. During the gas production period in 2020, there was a phenomenon of wellhead uplift. In order to ensure the safe production of the well, construction began from May 2021 and ended in July 2021. The successful implementation of this well has important reference and guidance significance for the replacement of casing heads in other wells of the gas storage.

Tepidibacillus marianensis sp. nov., a novel heterotrophic iron-reducing bacterium isolated from Mariana Trench sediment.

A novel chemoheterotrophic iron-reducing micro-organism, designated as strain LSZ-M11000T, was isolated from sediment of the Marianas Trench. Phylogenetic analysis based on the 16S rRNA gene revealed that strain LSZ-M11000T belonged to genus Tepidibacillus, with 97 % identity to that of Tepidibacillus fermentans STGHT, a mesophilic bacterium isolated from the Severo-Stavropolskoye underground gas storage facility in Russia. The polar lipid profile of strain LSZ-M11000T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, as well as other unidentified phospholipids and lipids. The major fatty acids were C16 : 0 (28.4 %), C18 : 0 (15.8 %), iso-C15 : 0 (12.9 %), and anteiso-C15 : 0 (12.0 %). Strain LSZ-M11000T had no menaquinone. Genome sequencing revealed that the genome size of strain LSZ-M11000T was 2.97 Mb and the DNA G+C content was 37.9 mol%. The average nucleotide identity values between strain LSZ-M11000T and its close phylogenetic relatives, Tepidibacillus fermentans STGHT and Tepidibacillus decaturensis Z9T, were 76.4 and 72.6 %, respectively. The corresponding DNA-DNA hybridization estimates were 20.9 and 23.4 %, respectively. Cells of strain LSZ-M11000T were rod-shaped (1.0-1.5×0.3-0.5 µm). Using pyruvate as an electron donor, it was capable of reducing KMnO4, MnO2, As(V), NaNO3, NaNO2, Na2SO4, Na2S2O3, and K2Cr2O7. Based on phenotypic, genotypic, and phylogenetic evidence, strain LSZ-M11000T is proposed to be a novel strain of the genus Tepidibacillus, for which the name Tepdibacillus marianensis is proposed. The type strain is LSZ-M11000T (=CCAM 1008T=JCM 39431T).

Monitoring urban construction and quarry blasts with low-cost seismic sensors and deep learning tools in the city of Oslo, Norway

The aim of this study is to collect information about events in the city of Oslo, Norway, that produce a seismic signature. In particular, we focus on blasts from the ongoing construction of tunnels and under-ground water storage facilities under populated areas in Oslo. We use seismic data recorded simultaneously on up to 11 Raspberry Shake sensors deployed between 2021 and 2023 to quickly detect, locate, and classify urban seismic events. We present a deep learning approach to first identify rare events and then to build an automatic classifier from those templates. For the first step, we employ an outlier detection method using auto-encoders trained on continuous background noise. We detect events using an STA/LTA trigger and apply the auto-encoder to those. Badly reconstructed signals are identified as outliers and subsequently located using their surface wave (Rg) signatures on the seismic network. In a second step, we train a supervised classifier using a Convolutional Neural Network to detect events similar to the identified blast signals. Our results show that up to 87% of about 1,900 confirmed blasts are detected and locatable in challenging background noise conditions. We demonstrate that a city can be monitored automatically and continuously for explosion events, which allows implementing an alert system for future smart city solutions.

Terrestrial laser scanning in the construction of a numerical model geometry related to underground post-mining facility

Abstract The procedure of building a quasi-3D geometry of a numerical model of an underground post-mining facility is presented in the article. For this purpose, measurements were made, based on the terrestrial laser scanning (TLS) technology, of a fragment of St. John adit, which is part of the underground tourist route “Geopark” St. Johannes Mine in Krobica in Lower Silesia in Poland, in the neighborhood of Krobica, Gierczyn and Przecznica – the places located in the vicinity of the well-known health resort Świeradów Zdrój. TLS, as one of the most advanced mining surveying technologies, enables accurate mapping of even the most complex geometries of underground mining facilities. This opens wide possibilities in the construction of more accurate numerical models of the behavior of the rock mass around such underground objects. As a result, more reliable calculation results are obtained, which are the basis for designing mining support protection, for example, with rock bolting. This translates into an improvement in the safety of underground excavations, in the conditions of exploitation in mining as well as in historical post-mining excavations made available to tourists. In the construction of the geometry of numerical model, software such as Trimble RealWorks was used to orientate individual “point clouds” from measurement stations. CloudCompare software was also used to generate cross sections to the adit axis, and AutoCad software was used for processing and spatial orientation of a selected characteristic cross section. Using the latest version of the FLAC 3D v.9.0 software, the excavation cross-section geometry obtained from measurements was mapped to and discretized (i.e., meshed), giving it a third dimension at the same time.

PROSPECTS FOR THE USE OF GAS TURBINE CENTRIFUGAL COMPRESSOR UNITS AT OIL AND GAS FACILITIES

The article is devoted to the study of gas turbine compressor units and, on the basis of this, the determination of technological, parametric and specific criteria and features of the use of gas turbine centrifugal compressor units in gas transmission systems and underground gas reservoirs. For this purpose, the advantages and disadvantages of gas turbine compressor units are analyzed. Comparative information is provided on the use of centrifugal, piston and screw compressors, which are often used in the oil and gas industry. The influence of the supply limit and supply volume, production time, and maintenance procedures on the choice of compressor type is shown. shown. A number of gas turbine compressor stations currently operating in Azerbaijan have been reported. The problems of gas lift operation of wells and the use of gas turbine centrifugal compressor devices in gas transmission systems and underground gas storage facilities have been studied from the point of view of technological, parametric and specific criteria, the unique characteristics of each system have been determined, and the unique characteristics of each system have been determined. Recommendations for pre-design studies have been developed for the purpose of using gas turbine centrifugal compressor devices in various systems. Keywords: gas turbine, compressor, gas lift system, gas transport, underground gas storage.

INNOVATIVE TECHNOLOGY FOR THE CONSTRUCTION OF A PYLON STATION OF THE METRO BASED ON THE EXPERIENCE OF USING NATM

Purpose. For quite a long time, the metro station of the pylon type of deep contour interval was considered an underground structure that no longer has development potential. However, after the introduction of innovative technologies during the construction of the Dnipro metro, in particular the New Austrian Tunneling Method (NATM), this design is being used again and has developed further use. The purpose of the scientific article is to analyze innovations in the technology of construction of a three-vaulted pylon metro station from precast reinforced concrete using NATM, which require scientific justification. Methodology. In order to achieve the goal, the traditional technology of constructing a deep contour interval pylon station was revised. An analysis of the features of NATM, which allow it to be used during the construction of a pylon station in strong rock, has been carried out. A step-by-step analysis of the construction of the station was implemented with the involvement of mathematical modeling based on the finite element method. For this purpose, a number of finite-element models of each stage of construction of a pylon-type station have been created. After the numerical analysis, the indicated models were adjusted in accordance with the changes associated with the new construction technology. Findings. The value of the stress-strain state of the pylon station was obtained during the numerical analysis of each stage of construction. Stress analysis proves the possibility of applying innovative construction technology in the case of a pylon station. Originality. On the basis of the performed numerical analysis of the phased construction of a pylon station based on NATM, dependencies were obtained that allow revising the existing concept of the construction of this type of station in strong rocks. The obtained data justify the application of NATM and release the potential of the analyzed underground structure. Practical value. The substantiation of the innovative technology based on NATM allows expanding the scope of its application and successfully carrying out the construction of such complex underground facilities.

A data-informed assessment method for the urban underground complex vitality

The urgent need for urban renewal and the rapid expansion of underground spaces has spurred the construction of urban underground complexes (UUCs). Vibrant UUCs are crucial for the efficient utilization of underground spaces and urban sustainability. Previous research on urban underground complex vitality (UUCV) has been primarily theoretical with limited reusability. In this study, we aimed to address this gap by focusing on underground functional facilities and spatial distribution characteristics to establish a UUCV indicator system based on walkability theory. We introduced a method based on exponential weighted mean for weight allocation to facilitate vitality calculations. Using the Wujiaochang UUC in Shanghai as a case study, we explored the spatial distribution mechanism of vitality and validated the feasibility of this research framework. The proposed assessment method and results obtained in this study offer valuable insights into underground space planning and design, particularly in the context of urban renewal.

A risk assessment approach for road collapse along tunnels based on an improved entropy weight method and K-means cluster algorithm

Ground collapse often occurs when strata are disturbed, particularly during tunnel construction, threatening the safety of people and underground facilities. Therefore, evaluating the risk of road collapse during and after tunnel construction is essential. Considering this, an improved entropy weight method was adopted to establish an evaluation system for assessing the collapse risk level of the Qianjin West Road, through which the Kunshan metro line S1 passes. The main implementation steps of the evaluation system include ten assessment indices, data visualization of indices, weight determination for indices, a cluster algorithm for the classification of results, and analysis of the evaluation results. In contrast to the traditional single method, and to improve the reliability of the risk assessment results, the method proposed in this paper considers two aspects. First, to eliminate subjective or objective biases generated by a single evaluation method, the entropy weight method (EM) and analytic hierarchy process (AHP) were integrated to formulate the improved entropy weight method. Second, to divide the evaluation results more reasonably, the k-means cluster algorithm using the Calinski Harabasz method was applied. The reliability and accuracy of the proposed improved entropy weight method are verified based on the case of Line S1. Furthermore, a method comparison and the concept of the coefficient of variation method were adopted to demonstrate the reliability of the risk assessment results. The improved entropy weight method can be used to evaluate ground collapse risk levels during and after tunnel construction.

Data driven assessment of rock mass quality in red-bed hilly area: a case study of Guang’an city, SW China

The evaluation of geological suitability for urban underground space (UUS) development is an indispensable prerequisite for its optimal utilization. As the actual carrier of underground facilities, the evaluation of rock mass quality plays a crucial role in assessing geological suitability. However, it is notable that the evaluation of rock mass quality has regrettably remained somewhat marginalized within the broader framework of the geological suitability assessment in recent years. The selection of pertinent indicators for the evaluation of rock mass quality inherently presents an appreciable degree of subjectivity. Predominantly subjective evaluation methods continue to dominate the field, while the application of objective algorithms, such as unsupervised clustering, remains in its nascent stage. Furthermore, there is a lack of comprehensive investigations into distinct combinations of attributes. This limitation confines the broader applicability of the evaluation outcomes in the context of urban underground space. Within this study, we meticulously amassed rock core test data from over 40 boreholes of engineering geological significance within the urban planning ambit of Guang'An City. Utilizing the K-means unsupervised clustering algorithm and the Principal Component Analysis (PCA) algorithm. We successfully conducted an unsupervised clustering procedure with nine distinct physical and mechanical attributes. This yielded an aggregation into five discernible clusters. Building upon the derived clustering outcomes, a stratification of rock mass quality was effectuated into three distinct tiers: Level 1 (characterized by pure sandstone), Level 2 (primarily dominated by sandstone), and Level 3 (denoting fair conditions predominantly influenced by mudstone). This structured stratification facilitates a relatively objective and comprehensive evaluation of rock mass quality within the context of the red-bed hilly terrain. In the course of this analytical trajectory, we conducted a dissection of the clustering efficacy. For strongly correlated attributes, we propose a preliminary dimensionality reduction procedure prior to the clustering endeavor. Moreover, we recommend intervals of 10 m for the stratified evaluation in red bed hilly urban terrains.

Evolution of stress field and plastic failure characteristics non-isobaric narrow gas storage spaces

The uncertainty of stress distribution and plastic damage threatens the safety of underground gas storage facilities. The bi-directional computational mechanics model is established first, the analytical solution for stress calculation and the implicit equation of plastic zone boundaries are derived. Then, the distribution of stress field in non-isobaric narrow gas storage spaces are studied, and the distribution law of plastic zone is revealed. The results show that: (1) The analytical solution of the surrounding rock of the non-isobaric gas storage roadway is derived, and the implicit equation of the boundary of the plastic zone is obtained; (2) The maximum principal stress exhibits an axisymmetric distribution, gradually decreasing with the increase of the distance; (3) As the stress P0 increases, the pressure equilibrium point increases; as λ increases, the pressure equilibrium point decreases first and then increases; (4) λ is more sensitive to roof failure than the two gangs; When λ is less than 1, the “elliptical” plastic zone appears at the roof, manifested as tensile and shear failure; when λ is 1, the “circular” plastic zone appear, manifested as shear failure; when λ is greater than 1, the elliptical plastic zone appears at the both sides, manifested as shear failure.

Automated processing of well logging data to monitor the position of the gas-water contact in underground gas storage facilities

Natural oil and gas deposits in most fields include some fluid contacts, such as oil–water, gas–water, or gas–oil. Monitoring the position of the gas–water contact in underground gas storage (UGS) facilities is crucial for monitoring the safety of the subsurface environment. As UGS facilities are geological features of long-term operation, the condition of these features must be regularly monitored for possible gas leaks due to various reasons, whether geological or technical. Periodic surveys of production wells using geophysical methods make it possible to timely detect the reasons for abnormal technical conditions and higher-than-normal water cuts of reservoirs, and to assess shifts in gas–water contact. The suite of production logging methods for surveying and monitoring underground gas storage facilities includes nuclear logging with the use of steady radiation sources (i.e., gamma ray logging and neutron logging). Analysis and interpretation of these methods make it possible to track the shift over time of the gas–water contact in gas-saturated sandstones with an interparticle porosity of >15%. Data from nuclear logging, temperature logs, and composition-based and flow-based surveying are processed and interpreted with the use of known methods and diagnostic indicators to achieve the following goals: to determine the intervals of inter-reservoir and behind-the-casing fluid movement on the base of the well log, to assess the technical condition of the wellbore, to monitor the position of the gas–water contact in the reservoir, to assess the gas saturation of the reservoir, and to monitor the thickness and integrity of the clay caprocks of UGS facilities [1]. This paper discusses the results of automated processing and interpretation of well data recorded during the survey of an UGS facility to determine the current position of the gas–water contact in the reservoir and the gas–water interface in the well. Quantitative interpretation of the neutron logging data with the use of steady radiation sources was performed, and the current gas saturation factor was estimated. Keywords: gas–water contact (GWC); gas saturation; underground gas storage; processing algorithm; gas–water interface (GWI).