Analysis of Casing Failure Associated with Bedded Salt Cavern Gas Storage

The mechanical properties and creep characteristic parameters of bedded rock salt were obtained by uniaxial and triaxial tests stimulating underground conditions. The bedded rock salt samples used in the experiments were got from H-10 well of a salt cavern gas storage in China. The "casing-cement-rock salt" numerical model was established to calculate the external pressure subjected to completion casing in bedded rock salt formation. Basing on the model, the influences of formation dip, interlayer friction coefficient, and creep time on the casing stresses and deformations were studied. The calculated results show that the external pressures are related to the angle between principal stress, location, and creep time. The maximum external pressure produced by creep is larger about 10% than in-situ stress. When the formation dip is smaller than about 50°, the stresses and deformations of casing increase with the formation dips, and which achieve the maximum at about 50°, and then decrease. The stresses and deformations decrease as the increase of interlayer friction coefficient.