Research on the Stability and Treatments of Natural Gas Storage Caverns With Different Shapes in Bedded Salt Rocks

Because of complex geo-conditions, many caverns by solution mining in bedded salt rocks have different irregular shapes. To verify the feasibility of using irregular-shaped caverns for underground gas storage (UGS), four typical cavern-shapes are selected, and the stability of each type is evaluated and compared by using the numerical simulation methods. The simulation results show that the UGS salt cavern with irregular wall shape has the lowest volume shrinkage and displacement of the wall rock, but larger plastic zones appear in their overhanging and concave parts. Ellipsoid-shape cavern has the best stability. Cylinder-shape cavern and cuboid-shape cavern have the poorest stability. In these two types of caverns, large deformations occur in the roof and sidewall, which pose a great potential of inducing collapse in the wall rock. By comparison of the stability characteristics in different positions of the wall rock, we found that the roof shape has a much greater influence than the sidewall on the stability of a cavern. The roof must be designed as an arch to improve cavern stability. Treatments to improve the stability of irregularly shaped caverns by changing operational pressure and utilization way or by modifying the caverns' shape are also discussed. So, this study not only determined the stability state of different shaped caverns for gas storage in bedded salt rocks, but also provides the ways to modify the irregular-shaped caverns for storage applications.