Long term creep closure of salt cavities

Cornet, Jan; Dąbrowski, Marcin; Schmid, Daniel W.

doi:10.1016/j.ijrmms.2018.01.025

Cited by 33 publications

(7 citation statements)

References 48 publications

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“…Generally, rock salt caverns are made through solution mining in formations at depths between around 200 and 2000 m. Greater depths would lead to significant creep and cavern closure, as a larger pressure difference causes a greater cavern shrinkage rate (Zhang, Wang, et al, 2018). The rate of cavern closure is strongly dependent on grain size, with much higher rates for fine grained rock salt caused predominantly by pressure solution creep (Cornet et al, 2018). Caverns at shallower depths may be prone to catastrophic failure.…”

Section: Undergrond Gas Storage In Rock Salt Cavernsmentioning

confidence: 99%

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Mineralogy, microstructures and geomechanics of rock salt for underground gas storage

Vandeginste

Buysschaert

et al. 2023

Deep Underground Science and Engineering

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Rock salt has excellent properties for its use as underground leak‐proof containers for the storage of renewable energy. Salt solution mining has long been used for salt mining, and can now be employed in the construction of underground salt caverns for the storage of hydrogen gas. This paper presents a wide range of methods to study the mineralogy, geochemistry, microstructure and geomechanical characteristics of rock salt, which are important in the engineering of safe underground storage rock salt caverns. The mineralogical composition of rock salt varies and is linked to its depositional environment and diagenetic alterations. The microstructure in rock salt is related to cataclastic deformation, diffusive mass transfer and intracrystalline plastic deformation, which can then be associated with the macrostructural geomechanical behavior. Compared to other types of rock, rock salt exhibits creep at lower temperatures. This behavior can be divided into three phases based on the changes in strain with time. However, at very low effective confining pressure and high deviatoric stress, rock salt can exhibit dilatant behavior, where brittle deformation could compromise the safety of underground gas storage in rock salt caverns. The proposed review presents the impact of purity, geochemistry and water content of rock salt on its geomechanical behavior, and thus, on the safety of the caverns.

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Section: Undergrond Gas Storage In Rock Salt Cavernsmentioning

confidence: 99%

“…The rate of cavern closure is strongly dependent on grain size, with much higher rates for fine grained rock salt caused predominantly by pressure solution creep (Cornet et al, 2018). Caverns at shallower depths may be prone to catastrophic failure.…”

Section: Rock Salt Cavern Depth Shape and Microstructuresmentioning

confidence: 99%

Mineralogy, microstructures and geomechanics of rock salt for underground gas storage

Vandeginste

Buysschaert

et al. 2023

Deep Underground Science and Engineering

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“…1a). The Carpathians are an Alpine orogen that records the late Jurassic to middle Miocene closure of the Alpine Tethys ocean (Sȃndulescu, 1988(Sȃndulescu, , 1984Csontos and Vörös, 2004;Schmid et al, 2008;Matenco, 2017). This thinskinned mountain belt is located at the contact between the Southern Carpathians and the Moesian platform (Fig.…”

Section: Regional Setting In Carpathian Geologymentioning

confidence: 99%

Rheological stratification in impure rock salt during long-term creep: morphology, microstructure, and numerical models of multilayer folds in the Ocnele Mari salt mine, Romania

et al. 2021

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Abstract. At laboratory timescales, rock salt samples with different composition and microstructure show variance in steady-state creep rates, but it is not known if and how this variance is manifested at low strain rates and corresponding deviatoric stresses. Here, we aim to quantify this from the analysis of multilayer folds that developed in rock salt over geological timescale in the Ocnele Mari salt mine in Romania. The formation is composed of over 90 % of halite, while distinct multiscale layering is caused by variation in the fraction of impurities. Regional tectonics and mine-scale fold structure are consistent with deformation in a shear zone after strong shearing in a regional detachment, forming over 10 m scale chevron folds of a tectonically sheared sedimentary layering, with smaller folds developing on different scales in the hinges. Fold patterns at various scales clearly indicate that during folding, the sequence was mechanically stratified. The dark layers contain more impurities and are characterised by a more regular layer thickness compared to the bright layers and are thus inferred to have higher viscosities. Optical microscopy of gamma-decorated samples shows a strong shape-preferred orientation of halite grains parallel to the foliation, which is reoriented parallel to the axial plane of the folds studied. Microstructures indicate dislocation creep, together with extensive fluid-assisted recrystallisation and strong evidence for solution–precipitation creep. This provides support for linear (Newtonian) viscous rheology as a dominating deformation mechanism during the folding. Deviatoric stress during folding was lower than during shearing in the detachment at around 1 MPa. We investigate fold development on various scales in a representative multilayer package using finite-element numerical models, constrain the relative layer thicknesses in a selected outcrop, and design a numerical model. We explore the effect of different Newtonian viscosity ratios between the layers on the evolving folds on different scales. By comparing the field data and numerical results, we estimate that the effective viscosity ratio between the layers was larger than 10 and up to 20. Additionally, we demonstrate that the considerable variation of the layer thicknesses is not a crucial factor to develop folds on different scales. Instead, unequal distribution of the thin layers, which organise themselves into effectively single layers with variable thickness, can control deformation on various scales. Our results show that impurities can significantly change the viscosity of rock salt deforming at low deviatoric stress and introduce anisotropic viscosity, even in relatively pure layered rock.

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“…The particular properties of rocksalt, including low density, low permeability, especially very low creep strength, play a key role in the stability of storage caverns (Chen et al, 2014;Jian-feng et al, 2015). After the excavation of underground storage, the surrounding rock will experience long-term time-dependent deformation, which seriously threatens the long-term stability of underground caverns (Cornet et al, 2018;Hou, 1997). Previous experimental researches have focused on the shortterm and long-term creep behavior of rocksalt, while mudstone often exists as caprock or interlayer in storage caverns (Liu et al, 2015;Wei et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Study on long-term uniaxial compression creep mechanical behavior of rocksalt-mudstone combined body

Lyu

Liu

Ren

et al. 2021

International Journal of Damage Mechanics

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Rocksalt and mudstone are usually under common stress in salt storage caverns, resulting in different mechanical properties from pure rocksalt and mudstone. To accurately obtain the creep mechanical characteristics of rocksalt-mudstone combined body, we have made three different combinations. The long-term creep experiment of bedded rocks can more closely reflect the long-term mechanical behavior of surrounding rock of salt storage caverns. The experimental results indicated that the long-term creep curve of the combined body includes initial and steady creep stages, and even includes accelerated creep stage. The strain of mudstone layer in the combined body was lower than that of rocksalt because of the higher strength. With the increase of the height ratio of mudstone, the creep strain of the combined body and each rock layer decreased, but the creep rate increased. A new nonlinear creep-damage constitutive model was proposed, which can well describe the creep evolution characteristics of the experiment. Compared with the fitting curves of classical Burgers and Nishihara creep constitutive models, it is revealed that the proposed model is most consistent with the experimental data. The duration of the long-term creep experiment under lower stress has a highly significant effect on the accuracy of predicting rock creep results. This research will contribute to a deeper understanding of the long-term creep characteristics of bedded rocks in salt storage caverns.

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Long term creep closure of salt cavities

Cited by 33 publications

References 48 publications

Mineralogy, microstructures and geomechanics of rock salt for underground gas storage

Mineralogy, microstructures and geomechanics of rock salt for underground gas storage

Rheological stratification in impure rock salt during long-term creep: morphology, microstructure, and numerical models of multilayer folds in the Ocnele Mari salt mine, Romania

Study on long-term uniaxial compression creep mechanical behavior of rocksalt-mudstone combined body

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