Large-scale compressed air energy storage facilities offer one solution to the UK's energy demands, using solution-mined caverns in salt lithologies. For optimum gas storage efficiency, cavern geometry should ideally be smooth: spherical to cylindrical with a circular cross-section. However, such caverns are often irregular with marked asymmetry or ellipticity, and whilst the reasons for non-circular cross-sections developing during solution-mining in some caverns can be related to e.g. the presence of interbedded lithologies, in other instances they are not fully understood.
Cavities from dissolution experiments using five main end-member salt facies fabrics from the Triassic Preesall and Northwich Halite formations have been assessed to determine factors affecting cavity geometry, formation and variability in dissolution behaviour. Identical sets of experiments were performed on each fabric type, using two solution concentration strengths: brine and synthetic seawater.
Comparison of experimental results using a combination of analytical and imaging techniques show the extent to which the salt fabric and enhancement of features within the salt influences the resulting dissolution cavity. Observations show a visible increase in micropores within the adjacent halite matrix following dissolution. Smaller-scale features provide further insights into the dissolution processes, and salt fabric behaviour under different dissolution conditions.
Supplementary material: A detailed methodology is available at https://doi.org/10.6084/m9.figshare.c.4282454