A new Cosserat‐like constitutive model for bedded salt rocks

Abstract

SUMMARYSalt rocks are commonly used as geologic host rocks for storage of gas and crude oil, and are being considered for the disposal of radioactive waste. Different from the salt rock domes in many countries, the salt rock formations in China are usually laminar with many alternating layers, i.e. rock salt, anhydrite, and/or mudstone. Considering the unique stratigraphic characteristics of these salt rocks, a new Cosseratlike medium constitutive model is proposed in order to facilitate efficient modeling of the mechanical behavior of these formations. In this model, a new representative volume element, containing two different layers, is employed to simulate the compatibility of the meso-displacement between two different layers and also the bending effect. A new method for the deformation and failure analysis of bedded salt rocks is derived therefrom. Having the macro-average stresses, the conventional stresses in the different layers can be obtained in sequence. The conventional stresses can then be utilized in a routine way for the strength and failure analysis. For the initial numerical modeling, the new Cosserat-like medium is reduced to a transversely isotropic one. The simplified constitutive model for layered media is then implemented into FLAC3D codes. A test sample validates that the results by using the numerical model are in good agreement with that by using the built-in model, and the mesh size for the new model is reduced greatly. Finally, an application for the stability of oil storage caverns in deep thinly bedded salt rocks is carried out. The effects on convergence of storage caverns and on the failure of surrounding rock due to the presence of the mudstone interlayers (hard phase) are discussed in detail.

Investigation on the permeability characteristics of bedded salt rocks and the tightness of natural gas caverns in such formations

“…Due to the high safety margin (effectively avoiding accidents such as those due to lightning, war and terrorist attacks, etc. ), lower cost and less occupation of land, underground storage facilities have much more extensive utilizations compared to the aboveground steel/concrete tanks (Li et al, 2012). With the rapid development of the economy, the total consumption of natural gas of China was 1800 Â 10 8 m 3 in 2014, and will rise to 2340 Â 10 8 m 3 in 2020 (Wang et al, 2015a).…”

Feasibility analysis of using abandoned salt caverns for large-scale underground energy storage in China

“…Research results have been used in the site selection and construction of salt cavern gas storages in Jintan and Huaian city in Jiangsu province, Qianjiang and Yingcheng city in Hubei province, and Pingdingshan city in Henan province, China. These engineering applications have demonstrated the research results with good practical implementation results [8,[15][16][17][18][19][20]. Meanwhile, the China National Energy Administration formulated the ''twelfth five-year'' natural gas development plan in 2012, and invested 81.1 billion yuan to construct 24 UGSs to increase the ratio of working gas volume to gas consumption to 5% [21].…”

Study on the Tri-axial Time-Dependent Deformation and Constitutive Model of Glauberite Salt Rock under the Coupled Effects of Compression and Dissolution

“…The time-dependent properties of salt rock are of fundamental importance in predicting long-term evolution of strategic storage caverns for oil and gas and as well as nuclear waste disposal in China due to their characteristics of low permeability and porosity [7,8]. As salt rock exhibits pronounced creep characteristics even under relatively low loads, many efforts have been devoted to investigating the mechanical creep behavior of salt rock through laboratory experiments and theories [9][10][11][12][13][14][15]. Creep test is the direct method to research the creep properties of salt rock, and it has been adopted by scholars to observe the creep deformation and rock characteristics.…”

“…Creep test is the direct method to research the creep properties of salt rock, and it has been adopted by scholars to observe the creep deformation and rock characteristics. References [13,14] analyzed the influence of confining pressure on the creep properties based on larger amounts of uniaxial and tri-axial experimental data. The author of [16] compared and analyzed the creep deformation of glauberite, anhydrite, and argillaceous salt rock based on tri-axial creep test.…”