盐穴地下储气库水溶造腔管柱的动力稳定性试验研究

针对建设盐穴地下储气库在实施单井油垫法水溶造腔过程中经常出现的造腔管柱破损和失稳问题,开展了水溶造腔管柱的动力稳定性试验研究,结合现场调研和理论分析结果,揭示出管柱抗弯刚度、悬伸长度及过流面积等是影响管柱动力稳定性的关键参数。据此设计出悬臂管动力失稳物理模型试验装置,开展了水溶造腔管柱磨损和动力失稳的试验研究。试验中观察到5种力学响应现象:(1)水锤现象;(2)静力屈曲;(3)混沌运动;(4)"类悬臂管"受迫振动;(5)不同端部条件影响现象。试验结果表明,引起水溶造腔管柱液—固耦合失稳现象的主要原因包括:(1)造腔水流的波动性易引起水锤和受迫振动现象,超长的受限空间悬臂结构管柱易"放大"这种现象;(2)过大的造腔注水流量可能引起造腔管柱发生静力屈曲或混沌运动;(3)造腔管柱结构和力学特性对造腔管柱系统的稳定性和安全性有着重要影响。

Dynamic stability tests on tubing string for solution mining of a salt cavern UGS

When a salt cavern underground gas storage (UGS) is built by using the single-well oil pad method, the tubing string is prone to failure and instability during solution mining. In this regard, the dynamic stability of solution mining string was tested. The test results, together with the site survey and theoretical analysis results, indicate that the bending strength, the overhanging length and the open area of a pipe string are the key parameters affecting its dynamic stability. Accordingly, the physical model test device for simulating the dynamic instability of cantilever pipes was developed to test the wear and dynamic instability of the solution mining string. During the test, five mechanical responses were observed, including water hammer, static buckling, chaotic motion, "cantilever-pipe-like" forced vibration, and the effects of different ends. The fluid–solid coupling instability of the solution mining string is attributed to three factors. First, the fluctuation of the water for solution mining may result in the phenomena of water hammer and forced vibration, which is probably magnified by ultra-long cantilever string in the confined space. Second, too high water injection flow may lead to static buckling or chaotic motion in the solution mining string. And third, structure and mechanical properties of the solution mining string may greatly affect its stability and safety.