盐岩地下储气库注采气套管运行安全的物理模型试验研究

注采气套管结构是保证盐岩地下储气库注采气正常运行的重要枢纽，在盐岩地下储气库运行过程中，套管混凝土环极易因储库蠕变体积收缩而产生受拉破坏。因此，为了解套管混凝土环的受力和变形特性，采用三维地质力学模型试验技术，对江苏金坛盐岩地下储气库开展了不同采气速率、不同采气内压、储库失压等风险因素影响下的套管运行过程的物理模型试验，通过三维地质力学模型试验较好反映出储气库套管混凝土环的受力和变形特性。研究表明：（1）套管混凝土环的轴向拉应变随采气速率的增加而增大，为保证套管的运行安全，建议储气库的最大采气速率不超过0.65 MPa/d；（2）套管混凝土环的轴向拉应变和套管所受蠕变挤压应力随套管鞋离腔顶距离的减小而增大，为保证储气库运行安全，套管底部距离储库腔顶的距离应大于10 m：（3）套管所受蠕变挤压应力随采气内压的减小而显著增大，储气库的最低运行气压应大于3 MPa，并应最大限度地防止储气库出现失压事故。

Physical model test on operational safety of injection and recovery casing of underground salt rock gas storages

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.