Underground Gas Storage Facilities Research Articles

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).

Investigation of ground movements induced by underground gas storages via unsupervised ML methodology applied to InSAR data

The research explores the definition, formalization, and validation of a sound and rigorous methodology for analyzing a vast amount of satellite-based measures to geo-localize and quantify the ground movements induced by the storage of natural gas in underground formations. Time series decomposition analysis and unsupervised machine learning algorithms (partitive and hierarchical clustering) are adopted for processing, categorizing, and interpreting ground vertical movements from InSAR acquisitions. At the surface level, storage operations induce characteristic seasonal and cyclical movements, showing uplift during the injection period and subsidence during the withdrawal one. Consequently, the analysis of the solely sinusoidal component of the vertical movements (obtained via the time-series decomposition) turns out to be the key aspect of the proposed approach for handling the superposition of different ground movement sources, and consequently for clearly and reliably identifying the effects of underground gas storage (UGS) only.The proposed methodology was validated using two independent case studies in the Po Plain (northern Italy), a highly urbanized area affected by ground movements induced by several natural and anthropogenic causes, including underground gas storage facilities. For each case study, the methodology localizes one well-defined and confined area as the most affected by storage operations: this area corresponds to a cluster characterized by a high cohesion and by a seasonality phase coherent with the storage injection/withdrawal periods. The other clusters group areally wide-spread measurement points; the phase of their sinusoidal curves shows no time-coherency (or even phase opposition) with the seasonal storage operations. The results were verified via available independent information about the storage locations and were compared with the findings of previous research.

Changes in filtration and capacitance properties of highly porous reservoir in underground gas storage: CT-based and geomechanical modeling

The paper presents the results of comprehensive studies of filtration and capacitance properties of highly porous reservoir rocks of the aquifer of an underground gas storage facility. The geomechanical part of the research included studying the dependence of rock permeability on the stress-strain state in the vicinity of the wells, and physical modeling of the implementation of the method of increasing the permeability of the wellbore zone - the method of directional unloading of the reservoir. The digital part of the research included computed tomography (CT)-based computer analysis of the internal structure, pore space characteristics, and filtration properties before and after the tests. According to the results of physical modeling of deformation and filtration processes, it is found that the permeability of rocks before fracture depends on the stress-strain state insignificantly, and this influence is reversible. However, when downhole pressure reaches 7-8 MPa, macrocracks in the rock begin to grow, accompanied by irreversible permeability increase. Porosity, geodesic tortuosity and permeability values were obtained based on digital studies and numerical modeling. A weak degree of transversal anisotropy of the filtration properties of rocks was detected. Based on the analysis of pore size distribution, pressure field and flow velocities, high homogeneity and connectivity of the rock pore space is shown. The absence of pronounced changes in pore space characteristics and pore permeability after non-uniform triaxial loading rocks was shown. On the basis of geometrical analysis of pore space, the reasons for weak permeability anisotropy were identified. The filtration-capacitance properties obtained from the digital analysis showed very good agreement with the results of field and laboratory measurements. The physical modeling has confirmed the efficiency of application of the directional unloading method for the reservoir under study. The necessary parameters of its application were calculated: bottomhole geometry, stage of operation, stresses and pressure drawdown value.

Experimental and field studies of wave technology for bottomhole cleaning and clogging of permeable formations

The article presents the results of field experiments and field tests of wave technology for bottomhole cleaning and clogging of permeable formations. Acceleration of well construction time and avoidance of plugging (especially in gas wells) is extremely important nowadays. It is widely acknowledged that rock fractures occur due to the alternating motion of the flushing fluid, and it has significant implications for accelerating drilling processes and maintaining wellbore stability. This can be achieved through the wave motion of the flushing fluid. The experiments were conducted on a specialized installation that simulates downhole conditions, enabling the modeling of downhole processes. We created and tested various designs of wave generators to flush holes of bits with different types and sizes. Experimental evidence suggests that wave technology can aid in bottomhole cleaning and the creation of a colmatation screen. The wave action helps to keep the bottomhole zone and well walls clean, and significantly reduces the penetration of drilling fluid filtrate into the rock. The use of wave technology for bottomhole cleaning and permeable formation ringing shows great potential for oil and gas well construction. The sealing of the borehole space is crucial in the construction of Underground Gas Storage facilities.

Underground natural gas storage facility operations and well leakage events in the United States

Federal minimum safety standards for underground natural gas storage (UNGS) operations in the United States (U.S.) were set by the Pipeline and Hazardous Materials Safety Administration (PHMSA) in the aftermath of the 2015 Aliso Canyon well leakage incident. Beginning in 2017, these standards required operators of U.S. UNGS facilities to publicly report: 1) leakage events that meet established criteria for incidents; 2) annual details of well construction, maintenance, and integrity testing activities; and 3) the occurrence of leading indicators of leakage (i.e., safety-related conditions). We reviewed both PHMSA reports and previously published studies to compile a dataset of 53 well leakage events at UNGS facilities in the U.S. that align with the PHMSA reporting requirements. Casings (55.0%) and wellheads (32.5%) were the most common failed well components identified. Human intervention through incorrect operation or outside force damage was the most common (39.3%) cause of well leakage events. Well leakage events caused by corrosion resulted in significantly greater emissions than those with other causes. UNGS annual reports detailed operations at 406 UNGS facilities with 17,993 wells—14,469 were injection and the remainder monitoring. Of these wells, 11,446 (63.6%) were reported to have a design that is potentially susceptible to a single point of failure, which is more than three times the previous estimate. Additional information about the status and construction of individual wells is needed to confirm the number of operational wells with a single-point-of-failure design. These data would help regulators identify single-point-of-failure wells and ensure the elevated risks associated with them are appropriately mitigated by proposed risk management plans. Statistically significant differences in the characteristics of UNGS facilities that have and have not experienced well leakage events were observed among those operating in depleted hydrocarbon reservoirs. Depleted hydrocarbon UNGS facilities that experienced well leakage events were generally larger, which suggests that focusing regulatory inspections and reviews on these facilities may be justified. The UNGS data reported were not sufficient to build a predictive model that forecasts well leakage events. Modeling efforts were limited by the data reporting format, which requires UNGS operators to aggregate data by facility in their annual reports. Gathering and evaluating information for individual wells at UNGS facilities would be valuable and may provide additional insights into well leakage risks to better inform risk management planning efforts.

The European natural gas system through the lens of data platforms

European Union legislation obliges natural gas transmission system operators to publish key transport indicators on a transparency platform operated by the European Network of Gas Transmission System Operators for Gas (ENTSOG). Gas Infrastructure Europe (GIE) maintains similar transparency initiatives, providing data on the use of liquefied natural gas (LNG) terminals as well as underground gas storage facilities. These platforms have become a useful source of information for researchers, practitioners, and policy makers that is available to the general public at no cost. We demonstrate that these data platforms essentially represent an archive of the European natural gas system and how the security of supply situation of Europe can be monitored in almost real time by analyzing the evolution of flow patterns on a daily basis as well as longer time horizons. In particular, we show how the system has reacted to infrastructure expansions, disruptions, and an evolving geopolitical context.

Technologies used in natural gas dehydration: Problems and solutions

This article provides a thorough exploration of diverse technologies utilized in the dehydration of natural gas. These include glycol absorption, desiccant adsorption, solvent salt adsorption, chemical cooling, and hydrate suppression processes. The content delves into the merits of each technology, outlines common challenges encountered, and presents optimal solutions. Notably, the article focuses on the specific challenges arising from glycol absorption, particularly in select gas fields and underground gas storage facilities in Uzbekistan. This comprehensive examination of dehydration technologies, coupled with the in-depth analysis of solutions for glycol absorption issues, enhances our collective understanding of gas processing methodologies. By addressing the intricacies of each technology and proposing effective solutions, the article stands as a valuable resource for professionals and researchers immersed in the realm of natural gas dehydration. The insights offered contribute to refining and advancing gas processing strategies, making it an essential reference for those navigating the complexities associated with this critical aspect of the energy industry.

Study on microstructure change of underground gas storage facilities and its influence on permeability

Study on microstructure change of underground gas storage facilities and its influence on permeability

Revealing patterns in the influence of variable permeability of well bottomhole zones on the operational modes of underground gas storage facilities

The object of this study is underground gas storage facilities (UGSF). The main problem being solved is to ensure effective management of the operation process of underground gas storage facilities (UGSF) at operational and forecast time intervals. One of the main factors that affect the operating modes of UGSF is significantly non-stationary filtration processes that take place in the bottomhole zones of wells. The complexity of assessing the multifactorial impact on depression/repression around the wells affects both the speed and accuracy of calculating the mode parameters of UGSF operation. Analysis of the results of well studies revealed a significant area of uncertainty in the calculation of the filtration resistance coefficients of their bottomhole zones. A satisfactory accuracy of the result in the expected time was achieved by building a model of integrated consideration of the influence of the parameters of all the bottomhole zones of the wells on the mode of UGSF operation. It turned out that the integrated consideration of the impact on the parameters of the bottomhole zones of the wells neutralized the effect of significant changes in the filtration resistance coefficients of the wells and ensured a sufficient speed of calculation of UGSF operation modes. Simultaneous simulation of ten operating UGSFs under the peak mode of withdrawal the entire available volume of active gas takes no more than six minutes. The speed of simulation of filtration processes in the bottomhole zones of wells ensured finding the best of them according to one or another criterion of operation mode quality. As a result of the research, a model was built and implemented by software, which was tested under real operating conditions and provides optimal planning of UGSF operating modes for given time intervals. Its use is an effective tool for the operational calculation of current modes and technical capacity of UGSF for a given pressure distribution in the system of main gas pipelines. The performance of the constructed mathematical methods has been confirmed by the results of numerical experiments

Microbiological insight into various underground gas storages in Vienna Basin focusing on methanogenic Archaea.

In recent years, there has been a growing interest in extending the potential of underground gas storage (UGS) facilities to hydrogen and carbon dioxide storage. However, this transition to hydrogen storage raises concerns regarding potential microbial reactions, which could convert hydrogen into methane. It is crucial to gain a comprehensive understanding of the microbial communities within any UGS facilities designated for hydrogen storage. In this study, underground water samples and water samples from surface technologies from 7 different UGS objects located in the Vienna Basin were studied using both molecular biology methods and cultivation methods. Results from 16S rRNA sequencing revealed that the proportion of archaea in the groundwater samples ranged from 20 to 58%, with methanogens being the predominant. Some water samples collected from surface technologies contained up to 87% of methanogens. Various species of methanogens were isolated from individual wells, including Methanobacterium sp., Methanocalculus sp., Methanolobus sp. or Methanosarcina sp. We also examined water samples for the presence of sulfate-reducing bacteria known to be involved in microbially induced corrosion and identified species of the genus Desulfovibrio in the samples. In the second part of our study, we contextualized our data by comparing it to available sequencing data from terrestrial subsurface environments worldwide. This allowed us to discern patterns and correlations between different types of underground samples based on environmental conditions. Our findings reveal presence of methanogens in all analyzed groups of underground samples, which suggests the possibility of unintended microbial hydrogen-to-methane conversion and the associated financial losses. Nevertheless, the prevalence of methanogens in our results also highlights the potential of the UGS environment, which can be effectively leveraged as a bioreactor for the conversion of hydrogen into methane, particularly in the context of Power-to-Methane technology.

Serbian Energy Sector in a Gap Between East and West

Serbia's energy sector is heavily reliant on Russian influence. On the other hand, Serbia's status as a candidate country for joining the European Union (EU) membership requires active working toward diversifying energy sources of supply. In the past decade, Serbia has secured a reduced price for natural gas through a bilateral agreement with Russia, addressing the shortfall in its domestic production. The former agreement priced Russian gas at US$270 per thousand cubic meters and expired in 2021. The new deal links gas prices to crude oil and ranges between US$310 and US$408, maintaining its competitive position as one of Europe's lowest import prices. Furthermore, alongside the new gas pipeline for Russian gas exports, the EU is funding the construction of a new interconnector, both with entry points from Bulgaria. Serbia also faces significant dependence on crude oil, and this reliance is compounded by the inability to import it from Russia any longer. Opposite, Serbia is usually self-sufficient in electricity production which still remains under state ownership. The domestic exploration and processing of oil and gas, as well as the sole underground gas storage facility in Serbia, have partial ownership by Russian Gazprom while the transportation of gas is under the full control of the Serbian government. This Communication about the energy situation in the Republic of Serbia put particular emphasis on the evolving political dynamics in the global energy market with a specific focus on the Russia–Ukraine war. The topic is also linked to the contentious status of the southern Serbian autonomous province, recognized as an independent state by the majority of Western nations but not by Serbia. It is feared that Serbia's energy dependence on Russia could have significant ramifications for its EU candidacy.

Underground hydrogen storage in Germany: Geological and infrastructural requirements

Hydrogen storage is crucial for the success of the hydrogen economy. In addition to storage tanks and pipes the geological subsurface could also offer cost-effective solutions for storing large quantities of hydrogen in salt caverns, aquifers, and depleted hydrocarbon fields. However, experience with underground hydrogen storage is limited to salt caverns, which have size and space limitations. In this contribution we therefore define positive indicators for pore storage systems and estimate storage capacities based on national CO2 and natural gas storage assessments in Germany.
 With a focus on the geological assessment of potential storage horizons, we first define positive and cautionary indicators for safe storage operations on the basis of a thorough literature review, including theoretical and experimental studies. For example, we find that optimal storage conditions in terms of energy content and hydrogen quality are found in sandstone reservoirs in the absence of carbonate and iron-bearing accessory minerals at a depth of approximately 1100 m and a temperature of at least 40 °C. Porosity and permeability of the reservoir formation should be at least 20 % and 5x10-13 m2 (~500 mD), respectively. The pH of the brine should moreover fall below 6 and the salinity should exceed 100 mg/L in order to limit microbial activities and hydrogen solubility in brine water.
 
 Second, we estimate hydrogen storage capacities based on published natural gas and CO2 storage volumes [1,2] and their respective physical properties. These estimates provide an upper bound that is independent of the positive and cautionary indicators defined in here. Nevertheless, we show that up to 8 billion cubic metres, or 29 TWh energy equivalent of hydrogen could be stored in underground gas storage facilities if all natural gas were to be replaced by hydrogen (Figure 1). In addition, saline aquifers could offer storage capacities of 81.6 to 691.8 Mt of hydrogen, based on CO2 storage assesments [2]. This corresponds to 3.2 to 27.3 PWh of hydrogen energy equivalent. The majority of which (~95 %) is located in the North German Basin. Fig. 3 shows the distribution of all pore storages (active and inactive; red and grey dots) and saline aquifers (green shaded areas) comparing it to the planned grid expansion initiative IPCEI (important projects of common European interests) [3]. These capacities would meet predicted storage requirements in Germany considering industrial, transport, and heating demands of 34 to 667 TWh (final hydrogen demand in 2050) many times over [4].
 
 We conclude that pore storage systems could play a crucial role in the future German hydrogen infrastructure, especially in regions with large industrial hydrogen demand and likely hydrogen imports via pipelines and ships. We therefore recommend that future research focus on assessing the technical storage potential of these sites and their compatibility with planned hydrogen infrastructures and industrial demand.

CHALLENGES OF IMPLEMENTING THE UNDERGROUND GAS STORAGE PROJECT IN GEORGIA

The launch of the Southern European Gas Corridor, the real prospect of increasing gas transit volumes for Georgia, has made even more critical the need to build an underground gas storage facility in Georgia. The technical and economic evaluation of gas storage in different prospective locations has already been done, there is also a gas storage project. The prospects for the construction of a gas storage facility in Georgia, and the need for the existence of a gas storage facility as an important tool for the country's energy security are discussed in the article.

Underground storage of hydrogen and hydrogen/methane mixtures in porous reservoirs: Influence of reservoir factors and engineering choices on deliverability and storage operations

Seasonal storage of natural gas (NG), which primarily consists of methane (CH4), has been practiced for more than a hundred years at underground gas storage (UGS) facilities that use depleted hydrocarbon reservoirs, saline aquifers, and salt caverns. To support a transition to a hydrogen (H2) economy, similar facilities are envisioned for long-duration, underground H2 storage (UHS) of either H2 or H2/CH4 mixtures. Experience with UGS can be used to guide the deployment of UHS, so we identify and quantify factors (formation/fluid properties and engineering choices) that influence reservoir behavior (e.g., viscous fingering and gravity override), the required number of injection/withdrawal wells, and required storage volume, contrasting the differences between the storage of CH4, H2, and H2/CH4 mixtures. The most important engineering choices are found to be the H2 fraction in H2/CH4 mixtures, storage depth, and injection rate. Storage at greater depths (higher pressure), but with relatively lower temperature, is more favorable because it maximizes volumetric energy-storage density, while minimizing viscous fingering and gravity override due to buoyancy. To store an equivalent amount of energy, storing H2/CH4 mixtures in UHS facilities will require more wells and greater reservoir volume than corresponding UGS facilities. We use our findings to make recommendations about further research needed to guide deployment of UHS in porous reservoirs.

Biodiversity and Potential Activity of Microorganisms in Underground Gas Storage Horizons

The share of molecular hydrogen as a source of “green energy” is currently significantly increasing. It is proposed to use existing underground natural gas storage facilities to store large volumes of hydrogen. In Russia, depleted oil and gas fields (DOGFs) and deep aquifers are used for natural gas storage. The purpose of this work was to determine microbial diversity in DOGF and deep aquifers by cultural and 16S rRNA gene-based approaches and the effect of H2 on the growth of microorganisms from the underground gas storage (UGS) horizons. The composition of the microbial community inhabiting the formation water of the Peschano–Umetskoe depleted oil and gas reservoir was typical for microbial communities of oil reservoirs and included bacteria of the phyla Bacillota (Dethiosulfatibacter, Defluviitalea, Acetobacterium, Syntrophobotulus), Actinobacteriota (Dietzia, Rhodococcus), Spirochaetota (Sphaerochaeta), Pseudomonadota (Shewanella), and Bacteroidota (Petrimonas), together with methanogenic archaea of the phylum Euryarchaeota (Methanobacterium). In some formation water samples, the share of methanogens of the genus Methanobacterium reached 61.6% of the total community; these hydrogen-utilizing organisms may contribute to the formation of methane in the reservoirs used for the storage of molecular hydrogen. Microbial communities of UGSs located in aquifers were less diverse and abundant. Cultivable hydrogenotrophic sulfate-reducing, homoacetogenic, and methanogenic prokaryotes were retrieved from the studied aquifers and from the DOGF used for gas storage. Microorganisms present in the condensation and reservoir waters of the UGS facilities can influence the composition of the water and gas phase, and affect the host rocks and borehole equipment.

Evaluation of fault stability and seismic potential for Hutubi underground gas storage due to seasonal injection and extraction

The Hutubi gas field was put into production in 1998 and then converted into an underground gas storage (UGS) facility in 2013, and since then a cluster of earthquakes associated with seasonal injection and extraction activities have been recorded nearby. To evaluate the fault stability and seismic potential, we established a pseudo-3D geomechanical model to simulate the process of seasonal injection and extraction. Reservoir pore pressures from 1998 to 2019 were obtained through multiphase reservoir simulation and validated by history matching the field injection and production data. We then imported pore pressures into the geomechanical model to simulate the poroelastic perturbation on faults for over 20 years. The fidelity of this model was validated by comparing the simulated surface deformation with global positioning system (GPS) measured data. We used Coulomb failure stress (CFS) as the indicator for the likelihood of fault slippage. The simulation results show that the location of the induced earthquake cluster was within the positive Coulomb stress perturbation (ΔCFS) area, in which fault slippage was promoted. In addition, ΔCFS at the earthquake location kept increasing after the injection began. These findings could explain the induced earthquakes with the Coulomb failure stress theory. Furthermore, we conducted a parameter sensitivity study on the dominant factors such as the maximum operating pressure (MOP), frictional coefficient, and dip angle of the pre-existing fault. The results indicate that the magnitude of ΔCFS caused by seasonal injection and extraction decreases with distance; MOPs are constrained to 32.9, 36.2, and 39.5 MPa according to different ΔCFS thresholds; the critical dip angle ranges are 0–20° and 80°–100°; and strengthening the fault friction can either increase or decrease the seismic potential. This study can help determine the MOP for Hutubi underground gas storage (HTB UGS) and provide a framework for simulating the potential causes of induced seismicity for other sites.

CURRENT STATUS AND WAYS TO IMPROVE THE EFFICIENCY OF THE DEVELOPMENT OF "KALMAZ" UNDERGROUND GAS STORAGE FACILITIES (UGSF)

Geological structure of the "Kalmaz" oil and gas field, that is being studied since 1930, is located 100 km south-west of Baku, in the north-eastern part of the lower Kura depression. Information on geological structure, stratigraphy, tectonics, oil and gas content of the field etc. has been collected as a result of the search and exploration works carried out and structural and research wells drilled. The "Kalmaz" field was formed from the brachianticlinal fold with south-east direction from north-west. The structure is divided into separate blocks by tectonic faults, and the blocks are not interconnected. Data on stratigraphic affiliation, lithology and thickness of stratigraphic units of sediments participating in the geological section of the site were obtained on the basis of deep wells drilled here. Upper Miocene-Pont, Pliocene and Quaternary sediments are involved in the geological section of the site. Tectonically, Kalmaz brachianticlinal is located in the north-eastern part of the lower Kura depression, over the Kalameddin-Bandovan anticline zone, between Mishovdag in the West and Khidirli folding in the East. The Kalmaz structure is mainly stretched in the north-west – south-east direction, however in the western part the axis of elongation of the structure takes a close direction to the latitude circle. The structure is asymmetrical. North-east wing is upright (lying angle is 35-400) and short, the south-west wing is relatively low-leaved (22-300) and being extensive passes to the south-east Shirvan syncline. The geological aspects of the structure was complicated by a fault that cuts its elongation at a certain angle. In the western part, tectonic fault passes through the north-east wing of the structure and through the south-west wing in the eastern part. As a result of the change in the direction of the axis of the fault structure, which is being talked about, cuts off the north-eastern wing in the western part, almost perpendicular to its lengthway and passes to the neighboring Navahi syncline. As a result of the fracture, the north-eastern wing of the Kalmaz structure and the south-western pericline were broken and dropped due to other parts of the fold. It's worth to note, that the Kalmaz structure has a very complex structure. This is also denoted by the Kalmaz mud volcano located in the central part of the fold. Despite the study of the geological aspects of the site by various methods and the numerous wells drilled here, its deep tectonics and connection with neighboring Mishovdagh and Khidirli structures have not been sufficiently studied. Numerous natural oil and gas manifestations are found in the site due to mud volcano springs. The mud volcano, located in the arch part of the fold, is related to a disruption that cuts its north-east wing. There is an active oil and gas flow from the mud springs arranged on a line in the direction of this disruption. Gas discharge related to Absheron sediments was detected in the structural mapping wells No. 39, 40, 41, 42, 44, 46 drilled on this strip. In most of these wells, the gas discharge passed into the gas fountain and lasted for a long time. 40000 m3/day gas and oil was obtained from the bottom Absheron sediments in the search well No. 87/2 located in the research site. In the well No. 15, drilled in a tectonic block in the south-eastern part of the fold, oil with a daily output of 38-39 t was obtained from the IV horizon of the productive layer (PL). Gas with daily production of 22 200 thousand m3 was obtained from the upper horizon of the PL in the search and operation well No. 22, and of 180 thousand m3 was obtained from the IV horizon of the PL in the well No. 40. As a result of research and exploration drilling, the I, II, III, IV, V, VI horizons of Kalmaz site have been proven to contain oil and gas. These facts show that the Kalmaz site has great oil and gas prospects. It should be noted that the presence of rich oil and gas underground gas storage facilitiess in the not yet opened and insufficiently studied lower horizons of the productive layer is beyond doubt. For this reason, information on geological study, stratigraphy, oil and gas characteristics, development, well fund of Kalmaz field, the first underground gas storage facilities in Azerbaijan, was analyzed in the article and due to the fact that a number of problems arose during the joint exploitation of wells, it was proposed to develop the well by dividing it into horizons. Keywords: gas, underground gas storage facilities, horizon, well, gas injection.

IMPROVING THE EFFICIENCY OF RESPONSE TO GAS, OIL AND WATER SHOWS AND OPEN FOUNTAINS BY CREATING A VIDEO SURVEILLANCE SYSTEM FOR GAS WELL WORKOVER

The oil and gas industry is one of the most important branches of the national economy. It differs from other branches of the fuel and energy complex in high capital investments and long construction and operation periods. One of the main tasks in gas industry enterprise management is the most efficient use of capital investments, which requires the adoption of informed decisions in oil and gas asset management. Gas industry enterprises include a large number of hazardous production facilities, accidents and incidents at which are the most dangerous for both personnel and population in general, as well as for the industry companies themselves. Emergencies at facilities can lead to financial and reputational losses, as well as damage the health and life of people and the environment. Therefore, the issue of planning measures for prevention, as well as localization and elimination of the accident consequences, is considered one of the priorities.The presence of video surveillance at production facilities is an integral part of an integrated security system. High-quality video surveillance helps to identify deviations in automated processes in a timely manner and take measures to eliminate failures and violations. Timely and rapid response to emergency situations prevents the occurrence of an accident, as well as prevents socio-economic damage.The authors have conducted many studies in the sphere of analysis of the organization of localization and liquidation of emergency situations and the effectiveness of personnel response in emergency situations at hazardous production facilities. Besides, studies of video surveillance systems in Gazprom UGS LLC branches – Departments of Emergency Recovery and Well Overhaul – have been conducted. Gazprom UGS LLC is the only operator of 23 underground gas storage facilities on the territory of the Russian Federation. Most of the Company's production facilities are located at a considerable distance from settlements and other infrastructure facilities, which increases the response time to emergency situations, and as a result, may lead to an emergency situation. Therefore, it is necessary to constantly control and monitor the integrity of the system. The authors have made conclusions about the need to improve existing video surveillance systems and expand their use at other branches of the Company.

Integrating underground gas storage experience for CCS optimisation

Carbon capture and storage (CCS) sites require diligent assessments to account for potential leakage over time. Leakage pathways include both natural and engineered (e.g. wells) invoking the requirement for a structured technical analysis as part of a risk inventory. This paper focuses on lessons learnt from underground gas storage (UGS) sites to guide CCS technical workflows to handle natural geological risk elements. UGS facilities have been operating for over a 100 years. Their injection and withdrawal histories, by their very nature, test the complex changes that occur to the reservoir and cap-rock over time and provide valuable insight to demonstrate the feasibility of CCS and its potential for long-term storage. Geomechanical assessment of the reservoir and cap-rock requires an inventory of core material, log and seismic data with the aim of selecting the appropriate data to model the ability of that formation to contain a column of CO2. As supercritical CO2 is injected into the formation and pore pressure builds, the geomechanics of the reservoir needs diligent review to assess the potential to trigger failure on the cap-rock and pre-existing faults and fractures. UGS injection/withdrawal histories assist in the reservoir and overburden static and dynamic modelling along with designing a measurement, monitoring and verification process for CCS sites. Technical workflows, from seismic and static modelling to geomechanics and dynamic simulation and back to seismic for containment monitoring, are discussed that have been refined by UGS experience to benefit the selection of potential CCS sites.