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Volume loss and volume loss rate of an ellipsoid-shape cavern with 100,000 m³ at depth of 450 m on seasonal operations
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Stability analysis of salt caverns is a very complicated subject due to the coupled time-dependent thermo-mechanical behavior of salt during leaching and operational phase of the gas storage subjected to the cyclic loading. Because of purely plastic behavior of salt and the relevant convergence during injection and withdrawal, investigation of the...
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Citations
... [39]). Instead of using such empirical or microscale scientific models, analysts typically calibrate engineering-type salt constitutive models against monotonic experiments and utilize them in cyclic loading simulations, without ever calibrating and/or validating those models against cyclic loading experiments [40][41][42][43][44][45]. Nevertheless, intricate cyclic phenomena are known to occur, such as reverse creep [46] and creep-fatigue interactions [47], that likely have a substantial impact on hydrogen storage caverns. ...
Underground caverns in a salt dome are promising geologic features to store hydrogen because of salt’s extremely low permeability and self-healing behavior. The salt cavern storage community, however, has not fully understood the geomechanical behaviors of salt rock driven by quick operation cycles of injection-production, which may significantly impact the cost-effective storage-recovery performance of multiple caverns. Our field-scale generic model captures the impact of cyclic loading-unloading on the salt creep behavior and deformation under different cycle frequencies, operating pressure, and spatial order of operating cavern(s). This systematic simulation study indicates that the initial operation cycle and arrangement of multiple caverns play a significant role in the creep-driven loss of cavern volumes and cavern deformation. Our future study will develop a new salt constitutive model based on geomechanical tests of site-specific salt rock to probe the cyclic behaviors of salt precisely both beneath and above the dilatancy boundary, including reverse (inverse transient) creep, the Bauschinger effect, and damage-healing mechanism.
... (e.g. Heusermann et al. 2003;Zhang et al. 2015;Böttcher et al. 2017;Cała et al. 2018;Makhmutov et al. 2020, Habibi et al. 2021. Recent studies indicate, however, that diffusion creep can be essential for viscous deformation of rock salt, in addition to di-khmutov i in. ...
... The range of differential stresses in rock salt on perimeter of gas storage cavern depends on the level of gas fill and the cavern depth, which gives a range of several to few dozen MPas (e.g. Cała et al. 2018;Makhmutov et al. 2020;Cyran and Kowalski 2021;Habibi et al. 2021). The rock salt grain size between 1 and 20 mm is fairly typical for natural rock salt. ...
PL: Tempo konwergencji podziemnych magazynów solnych jest jednym z parametrów warunkujących ich długotrwałą stabilność. Pełzanie dyslokacyjne jest powszechnie uważane za główny mechanizm deformacji w solach kamiennych odpowiedzialny za konwergencję kawern. Jest to związane głównie z faktem, że mechanizm ten dominuje dla deformacji związanej z dużymi naprężeniami różnicowymi, które są spodziewane podczas eksploatacji takich kawern. Przedstawiona w artykule analiza wskazuje, że dla szerokich zakresów możliwych stanów naprężeń w magazynach pełzanie dyfuzyjne może być drugim istotnym mechanizmem deformacji. Jest to szczególnie istotne dla kawern, w których magazynowane są substancje gazowe, gdyż stan naprężeń waha się istotnie w zależności od poziomu wypełnienia gazem. Analiza danych z sześciu otworów wiertniczych na terenie wyniesienia Łeby wykazała, że przy uwzględnieniu pełzania dyfuzyjnego tempa odkształcenia, a co za tym idzie, tempa zaciskania się kawerny, w niektórych częściach profilu mogą być znacznie wyższe niż w przypadku obliczeń opartych wyłącznie na zjawisku pełzania dyslokacyjnego. Różnica ta może sięgnąć nawet kilku rzędów wielkości. Szczególnie istotną cechą jest tu rozmiar uziarnienia, który ma kluczowe znaczenie dla intensywności pełzania dyfuzyjnego. Przedstawione w artykule badania wskazują, że dla prawidłowej oceny tempa zaciskania się kawern istotne jest uwzględnienie dwóch mechanizmów deformacji zarówno pełzania dyslokacyjnego jak i dyfuzyjnego
EN: Convergence rate is one of the important parameters that control the long-term stability of underground storage caverns in rock salt. Dislocation creep is generally considered to be the main deformation mechanism responsible for the cavern convergence. This is related to the fact that for high differential stresses (that are expected to occur around the salt cavern) this mechanism dominates during the deformation. However, in this paper, we present an analysis showing that for ranges of probable differential stresses around the caverns, solution-precipitation creep can be also a significant deformation mechanism. It is of special importance for gas storage caverns, since the stress state around the cavern is highly dependent on the pressure of gas within the cavern that varies significantly throughout the injection-withdrawal cycle. Analysis of data from six selected boreholes located in the Łeba Elevation (northern Poland) shows that incorporating the solution-precipitation creep in the convergence rate can lead to significantly higher values as compared to the analysis when only dislocation creep is considered. The difference can reach several orders of magnitude. The grainsize is especially important since it strongly influences the pressure solution creep. The paper shows that for accurate prediction of cavern convergence rates, both dislocation and solution-precipitation creep should be employed in the study.
... Because rock salt is characterized by favorable rheology [2,3], low permeability [4,5], and self-recovery after damage [6], underground salt caverns are the optimal medium for the storage of hydrocarbons, including natural gas [7], oil, compressed air [8], hydrogen [9][10][11], and radioactive waste [12]. Compared with other reserve types for natural gas, including aquifers and depleted reservoirs, salt cavern gas storage is safer and has a higher percentage of cushion gas and a more flexible injection mode. ...
... Compared with other reserve types for natural gas, including aquifers and depleted reservoirs, salt cavern gas storage is safer and has a higher percentage of cushion gas and a more flexible injection mode. Unlike the salt domes in Germany and [9][10][11], and radioactive waste [12]. Compared with other reserve types for natural gas, including aquifers and depleted reservoirs, salt cavern gas storage is safer and has a higher percentage of cushion gas and a more flexible injection mode. ...
To increase natural gas storage capacity and further utilize salt mine resources, salt cavern gas storage in the Yunying salt mine, Hubei Province, China, was simultaneously constructed in two different mining layers (K3 and K4). The purpose of this study was to investigate the long-term feasibility of operating salt caverns for gas storage in two mining layers. Based on the geological conditions and sonar test results, the geometric parameters for the salt caverns in the two mining layers were designed, and a 3D geomechanical model was built to predict the cavern stability. The corresponding evaluation index included the displacement, volume shrinkage rate, equivalent strain, and dilatancy factor. The results show that simultaneously operating salt cavern gas storage in two mining layers is feasible, and the operational pressures for the salt caverns in mining layers K3 and K4 should be no less than 4-9 and 7-12 MPa, respectively, to satisfy the stability requirements. The surrounding rock of the salt caverns presents a larger displacement and volume reduction compared with cases in which the salt caverns are operated in a single mining layer. Increasing the injection-withdrawal frequency increases the deformation of the surrounding rock.
... Regarding the convergence, Habibi et al. [105] showed that considerable creep occurs even for the cases where the cavern is under maximum permissible pressure. It is because rock salt experiences non-linear deformation under low deviatoric stress. ...
... Various researchers, such as Bauer and Sobolik [110] and Staudtmeister et al. [100], have shown that effective tensile stress emerges in the surrounding rock. Since the tensile strength of rock salt is low (around 2 MPa [105]), it is possible for new fractures or pre-existing cracks to open during withdrawal. ...
... A 3D version of LOCAS was proposed, which modeled rock salt's thermal and hydraulic behavior simultaneously, among other features [118]. In 2021, Habibi et al. [105] applied LOCAS to simulate stress changes due to leaching and the thermo-mechanical and thermodynamic behavior of Iran's first salt cavern gas storage over a 10-year lifespan. ...
Salt formations are utilized to store hydrocarbons, hydrogen, compressed air, and nuclear waste disposal. The stability and integrity of these salt structures are crucial for ensuring environmental and operational safety. This is governed by the combined effect of Thermal-Hydraulic-Mechanical-Chemical (THMC) processes. It is necessary to classify the phenomena involved in each process and identify the parameters that significantly influence them to comprehend the coupled mechanisms. While field operations provide valuable insights, they must offer detailed knowledge of the coupled processes. Analytical and numerical methods are essential to adequately describe THMC processes and bridge this knowledge gap. This study presents the coupled THMC processes in energy storage stage, gas storage, and waste disposal in salt caverns. The objective is to identify the key parameters associated with each process. Additionally, the study investigates available codes and software that simulate these processes and phenomena. Their advantages and drawbacks are discussed. The outcome of this study will help to design a comprehensive framework that integrates software and codes, lab experiments, and field investigations. This framework will facilitate the enhancement of environmental and operational safety measures.
... Multiphysics coupling for salt cavern gas storage has also been considered. Thermomechanical simulations have been performed to study gas cycling conditions (Brouard et al., 2012;, the influence of cavern shape and buried depth (Habibi et al., 2021), and even cavern blowout (Djizanne et al., 2014). In contrast, a full THM (Thermo-hydro-mechanical) modelling of salt caverns is still scarce and very few studies are available, such as those by Asgari et al. (2020) and Fang et al. (2022). ...
The present work is devoted to the study of underground hydrogen storage in salt caverns. Based on the hydromechanical characteristics of rock salts obtained from some laboratory experiments, we propose a novel model that includes short- and long-term mechanical behaviour. Specifically, the short-term part incorporates the elastoplastic and instantaneous damage mechanisms. Concerning the long-term behaviour, in addition to the primary and secondary creep phases, the tertiary phase takes into account a delayed damage mechanism.
As application, we performed hydromechanical modelling of two vertical salt caverns with different depths based on existing hydrogen gas caverns, which are subjected to cyclic hydrogen injection and withdrawal (seasonal and daily scenarios). Gas transport is also modelled taking into account diffusion and advection mechanisms. Mechanical results indicate that the stability problem of a very deep cavern is more worrying in comparison with a shallow cavern, as expected. However, the gas extension is the same for both caverns because the gas flow is mainly by diffusion transport, while the permeability does not significantly increase. Since field data at very depths are limited, a sensibility analysis of material properties was carried out to provide insight into key mechanisms that may occur. Typically, a decrease in mechanical properties increases the extent of the damage around deep cavern but did not lead to significant increase in the extent of gas leakage. Under the assumptions made, these findings suggest that the use of salt caverns for green hydrogen storage, even with aggressive operating conditions to regulate variations between renewable energy production and peak power demands, should not significantly affect the stability of salt cavern nor promote an increase in hydrogen loss.
... Following Bérest's work, both experimental and numerical investigations were conducted to investigate the thermo-mechanical response of salt caverns during rapid cooling [11,12,13,14,15,16,17]. To ensure the integrity and stability of salt caverns, fractures, and rock damage should be avoided [18,19,20,21]. Rock damage is defined as the degradation of the macroscopic properties, such as strength, stiffness, etc [22,23,24]. ...
The integrity and stability of salt caverns for natural gas storage are subjected to a gas cycling loading operation. The coupled effect of confining pressure and temperature on the response of the salt cavity surrounding the wall is essential to stability analysis. In this study, a hybrid continuum-discrete model accounting for the thermal-mechanical process is proposed to investigate the thermal-damage evolution mechanism towards a field case with blocks falling off the salt cavity. The salt cavity is modeled by continuum zones, and the potential damage zones are simulated by discrete particles. Three specimens at different locations around the surrounding wall are compared in the context of severe depressurization. The dynamic responses of rock salt, including temperature spatiotemporal variation, microscopic cracking patterns, and energy evolution exhibit spatial and confinement dependence. A series of numerical simulations were conducted to study the influence of microproperties and thermal properties. It is shown that the evolution of cracks is controlled by (1) the thermal-mechanical process (i.e., depressurization and retention at low pressure) and (2) the anomalous zone close to the brim of the salt cavity surrounding the wall. The zone far away from the marginal surrounding wall is less affected by temperature, and only the mechanical conditions control the development of cracks. This continuum/discontinuum approach provides an alternative method to investigate the progressive thermal damage and its microscopic mechanism.
... Therefore, the deviatoric stress should be kept in a range in which the stability and integrity of the cavern can be ensured during the lifespan. Habibi et al. (2021) discussed some methods to address the issue of stress; for example, in caverns containing natural gas, the large deviatoric stress is neutralized by brine hydrostatic pressure during leaching and by gas pressure during operation. However, the pressure resulting from natural gas is not large enough to prevent dilation or fracturing around the cavern, so generally the internal pressure cannot totally overcome the lithostatic pressure. ...
... When the operating pressure reaches its maximum, healing of the rock salt takes place because there is enough time (from end of the injection to beginning of the withdrawal) during which there is almost hydrostatic pressure around the cavern owing to the low deviatoric stress. However, the healing cannot offset all the damage that occurred in the minimum-pressure state (Habibi et al. 2021). ...
... Salt rock samples from the Nasrabad dome in Kashan environs were used for tests. Preliminary tests on the rock salt samples carried out by Habibi et al. (2021) and elastic modulus and strength of the rock salt sample had been determined, which is presented in Table (1) [13]. Rock salt samples were prepared according to the ISRM standard [14]. ...
... Salt rock samples from the Nasrabad dome in Kashan environs were used for tests. Preliminary tests on the rock salt samples carried out by Habibi et al. (2021) and elastic modulus and strength of the rock salt sample had been determined, which is presented in Table (1) [13]. Rock salt samples were prepared according to the ISRM standard [14]. ...
Natural gas, air and oil materials can be stored in caverns, which are created in salt domes and have thick rock salt layers. These caverns may be subject to cyclic loading on a daily, weekly, and monthly basis due to the internal consumption of accumulated materials. The amount of deformation created over long periods of time effects the stability of the cavern. A number of models have been proposed to predict the long-term deformation of rock salt. One of these models is the Lubby2 model. In this research, the long-term behavior and stability of salt cavern storage under cyclic loading has been investigated. As a case study, the geometry of the German Hantorf salt cavern compressed air has been used. Salt rock properties of the Nasrabad Dome were considered. Creep tests were conducted on samples of rock salt at three stress levels in a stepwise manner and each test in different temperatures. Parameters of the Lubby2 model were determined. In order to investigate the effect of loading and unloading frequency on rock salt behavior, cyclic loading tests with different frequencies were also performed. For the purposes of this research, LOCAS finite element software with the Lubby2 model was utilized. A geometrical model of the cavern was built and executed in the software. The long term stability of the cavern and ground settlement were also investigated. tThe results showed that the Maxwell's viscoelastic coefficient in Lubby2 model is dependent on cycle loading frequency and it decreases exponentially with increasing loading frequency. Maxwell's viscosity coefficient decreases with increasing loading frequency. The deformation of cavern and ground subsidence with daily loading frequency has a rate of 10% and 8.6% higher than a cavern with constant loading, respectively. The effect of the cyclic load on Maxwell's viscoelastic coefficient was seen and the Lubby2 model was corrected for cyclic loading.
... Under the influence of stresses, both time-independent elastic deformations and time-dependent creep deformations appear in them [1,2]. In works [3,4] the necessity of applying measures to preserve bearing capacity of inter-chamber pillars at salt deposits is shown. In some cases, deformation of inter-chamber pillars may lead to occurrence of hydraulically connected system of cracks in water-protective strata (WPS) [5][6][7]. ...
... The use of the visco-elastic-plastic model of sylvinite behavior is caused by geomechanical processes in the salt rocks of inter-chamber pillars, which occur in a time perspective [4,20]. Deformation of inter-chamber pillars is determined by both stress value and strength, deformation and rheological properties of rocks. ...
The method of compliant fixing of inter-compartment pillars in the rocks prone to the exhibiting of rheological properties is presented in this article. The method of forecasting the deformations of anchored pillars is developed using the example of the development system of the tenth western panel of the AB formation, Verkhnekamskoe deposit of potassium-magnesium salts. Numerical realization of the model is performed by the finite element method in the software package Simulia Abaqus with the use of visco-elastic-plastic geomechanical model of sylvinite. Parametric support for the rheological model was made on the basis of the results of measurements of horizontal displacements of contour benchmarks interchamber pillars. The forecast was carried out for a period of 150 years after the chambers were fully developed. It has been established that the value of horizontal displacement of lateral surface of unlined interchamber pillars is equal to 123 mm for the forecast period. A comparative analysis of wire rope fastening operation with different rope diameters and fastener reaction values in the undercut mode of operation has been carried out. The exponential character of dependence between the duration of underlay and rigid regime of the roof support and the criterion of its effective work was revealed. It is evident from the presented data that the increase of the fastener efficiency increases with the use of a larger diameter rope, but the choice of the maximum rope diameter is limited by the design features of the fastener. The equation of dependence of horizontal displacements of the side surface of the anchored pillar on time and fastener reaction is given in the work. The forecast of the stress-strain state of the anchored pillars showed a positive effect of the supple support to increase the bearing capacity of the pillar both during its operation and after its destruction.
... Multiphysics coupling for salt cavern gas storage has also been considered. Thermomechanical simulations have been performed to study gas cycling conditions (Brouard et al., 2012;, the influence of cavern shape and buried depth (Habibi et al., 2021), and even cavern blowout (Djizanne et al., 2014). In contrast, a full THM (Thermo-hydro-mechanical) modelling of salt caverns is still scarce and very few studies are available, such as those by Asgari et al. (2020) and Fang et al. (2022). ...
