金坛A盐穴储气库体积收缩率较大原因分析

金坛盐穴储气库A溶腔投产不到2年，声呐测腔结果表明该腔体体积收缩率达到3.86%，约为该区域其他腔体体积收缩率平均值的5~7倍。为了找到该腔体体积收缩率过大的原因，根据金坛地层结构、声呐测腔数据和运行压力监测值等参数建立了用于该腔体稳定性评价的三维地质力学模型，对腔体体积收缩率、腔壁变形量、塑性区、等效应变和剪胀安全系数等稳定性评价指标进行了计算分析。计算结果表明:导致出现体积收缩率过大的主要原因是声呐测量误差而不是真实体积收缩，该腔体形状较为复杂，存在大量隐护空间，导致声呐测量误差增加；该腔体整体稳定性较好，腔体体积收缩率约为0.54%；该腔顶部结构较为平直且跨度大，不利于腔顶承载，一旦出现局部破坏，在自重作用下将会发生顶部掉块等失稳破坏，甚至威胁到套管鞋安全，建议在后期运行过程中加强监控。

Analysis on the reason for the higher volume shrinkage of Cavity A of Jintan salt-cavern gas storage

The Cavity A of Jintan Salt-Cavern Gas storage has been put into production for less than 2 years, but the sonar cavity test result shows that its volume shrinkage is 3.86%, which is about 5-7 times the average volume shrinkage of the other cavities in this area. In order to find out the reason for this excessive volume shrinkage, a 3D geomechanics model used for cavity stability evaluation was established based on stratigraphic structure, sonar cavity test data and monitored operation pressure in Jintan. Then, stability evaluation indexes were calculated and analyzed, including cavity volume shrinkage, cavity wall deformation, plastic zone, equivalent strain and dilation safety factor. It is indicated that the main reason for the excessive volume shrinkage is the sonar measurement error instead of the real volume shrinkage. The shape of this cavity is complicated with a great amount of hidden space, which increases the sonar measurement error. The cavity is overall more stable and its volume shrinkage is about 0.54%. The top structure of the cavity is flat with large span, which is not beneficial to the cavity top loading, so once it is damaged locally, instability damage (e.g. fallings from the top) will occur under the action of its dead weight and even the safety of the casing shoe will be threatened. Therefore, it is suggested to strengthen monitoring and control in the process of later operation.