The influence of cavern length on deformation and barrier integrity around horizontal energy storage salt caverns

Horizontal cavern structures are discussed as a means to constructing energy storage facilities in bedded salt formations. During their design, the spacing of injection and discharge boreholes for solution mining is an important variable determining cavern length, shape and construction cost, but also influencing the long-term mechanical behavior during the storage of oil or gas. Increasing the borehole spacing has been suggested in order to increase cavern capacity and construction rate while decreasing construction cost but its mechanical consequences have yet to be explored. In this paper, cavern geometries constructed with different borehole spacings are obtained using a solution mining simulation model. Static creep analyses have been conducted based on these geometrical models to discuss the impact of the maximum cavern length on the mechanical behavior of the caverns. The results show that the creep deformation of the horizontal cavern induces limited volume change depending on operating pressures. Increasing the length of the cavern initially increases cavern roof displacement and volumetric convergence, but plateaus after a length 600 m, i.e. 5 to 6 times the cross-sectional diameter. A similar behavior is observed in terms of selected integrity criteria. The results indicate the principal possibility to access larger storage volumes and higher construction speed by increasing the borehole spacing to longer than 5 to 6 times the designed cross-sectional diameter. (c) 2022 Elsevier Ltd. All rights reserved.