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| Setting method for operating pressure of underground gas storage bedded salt cavern |
| CHEN Xiangsheng1，XIONG Tiankai1，LI Yinping2，SHI Xilin2，ZHOU Donglin3 |
| (1. State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure，East China Jiaotong University，Nanchang，Jiangxi 330013，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；3. Salt Cavern of Gas Storage Technology Research Institute，PetroChina，Zhenjiang，Jiangsu 212000，China) |
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Abstract Operating pressure setting of underground salt cavern gas storage is not only concerns its long-term stability and tightness，but also affects the gas storage scale and peak shaving capacity. Therefore，determining the operating pressure interval is of great engineering significance for large-scale energy storage in salt caverns. To provide a basis for the operating pressure setting，taking the long-term safety of the cavern storage as the principle，the criteria for setting the maximum and minimum operating pressure with tightness and stability as the main control factors are summarized respectively. Based on the interaction mechanism between the surrounding rock and storage medium in salt cavern gas storage and the ultimate operating pressure setting criteria，a coupled fluid-solid analysis model considering damage and permeability evolution is established and applied to the simultaneous analysis of tightness and stability of an actual salt cavern gas storage reservoir through numerical development. The evolution laws and influencing factors of surrounding rock damage and permeability are discussed，and then several key design parameters of the target reservoir are determined，such as operating pressure interval，pillar width and salt roof thickness. The results show that the effects of operating pressure on the seepage range and creep shrinkage rate are diametrically opposed，in which the seepage range is positively correlated with the operating pressure in a power function relationship，and the creep shrinkage rate is negatively correlated with the operating pressure in an exponential function relationship. Therefore，the tightness determines the maximum operating pressure of a reservoir，and the stability controls the minimum operating pressure of a reservoir. Surrounding rock damage is mainly affected by stress level and rock deformation properties. Permeability evolution depends on the competing results of effective mean stress and plastic damage，and only when plastic damage dominates can the phenomenon of permeability surge be induced. The gas seepage range considering the permeability parameters evolution is approximately 5% larger than that without considering it. This impact is mainly concentrated within about 10 meters of the salt cavern boundary.
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