Abstract: The gas injection and recovery casing structure is an important hub to ensure the normal operation of underground salt rock gas storage. During the operation of gas storages, the casing concrete is vulnerable to tensile failure because of the volume contraction caused by creep. Therefore, in order to understand the mechanical and deformational characteristics of the casing cement ring, the three-dimensional geomechanical model test technology is adopted and the physical model test on operation process of Jintan salt rock gas storage casing under the influences of different risk factors including different gas recovery rates, different gas production pressures and cavern pressure loss is carried out. The 3-D geomechanical model test can reflect the mechanical and deformational characteristics of the concrete ring of gas storage casing better. The results show that: (1) the axial tensile strain of casing cement ring gets greater as the increase of gas recovery rate, in order to ensure the operation safety of the casing, the maximum gas recovery rate should be less than 0.65 MPa/d. (2) The axial tensile strain and the creep compressive stress acting on the casing increase with the decreasing of the distance between the casing shoe and the top of the cavern. In order to ensure the safety of the gas storage, the distance between the bottom of the casing and the top of the cavern should be more than 10 m. (3) The creep compressive stress acting on the casing increases significantly with the decrease of the gas production pressure, so the minimum operating pressure of storage should be more than 3 MPa, and the accident of pressure loss should be prevented to the minimum.

Key words: underground salt rock gas storage, casing for gas injection and recovery, stored gas pressure, gas recovery rate, geomechanical model test