Study On The Optimization Of The Construction Of Salt Cave Gas Storage In The Case Of Sandwich

Underground salt cavern gas storage is an important part of energy reserve in China. However, the study on gas storage remains an initial stage and this means that the practical experience of solving this problem is quite insufficiency. This cannot satisfy the requirement of gas storage’s design, construction and operation, and even we cannot find any official guidances of this currently. Although there exist advanced construction technologies of gas storage at overseas, these technologies cannot be applied in our studies directly because of the difference of salt rocks’geological characteristics between China and foreign countries. Especially, the development of interlayer is the main difference in terms of gas storage among all countries and this has a huge influence of the whole process duringsolution mining.Therefore, this paper mainly focuses on the influence of interlayer on solution mining process. Dissolutionmechanism of salt rock,interlayer’s properties and optimal design of gas storage’shape are discussed firstly. Then, the whole process during solution mining is simulated. Moreover, Proper orthogonal decomposition (POD) method can be introduced in the reconstruction and predictionof velocity during the same period. What’s more, cusp displacement catastrophe theory can be used in the stability evaluation of interlayer in cavity and the influence of this interlayer on the cavity’s shape during this period. The designed shape can be proved reasonably by the long term stability of this gas storage during the operation period.Main contents are as follows:The First:numerical simulation of salt cavern gas storage with interlayer during solution mining(1)The whole process during solution mining of realsalt cavern gas storage is simulated. Isograms of salt mass fraction in this cavity can be used to illustrate this process vividly.(2) A proper construction method can be obtained by the discussion among different parameters, including groups of construction and geologicalproperties.The Second:the reconstruction of fluid and fast prediction of parameters in this field(1) According to data samples in full model, single, double and tripleparameters are reconstructed in fluid field of the cavity during same periodrespectively by POD method.(2) POD method proposed can be proved fast and accurately to calculate velocity in the cavity by the comparison of results in full model and in this method.The Third:the study on stability of interlayer in the cavity during solution mining(1) Cusp displacement catastrophe theory can be introduced to propose the new theoretical calculation methods and numerical models towards instability failure of interlayer. A specific example can be used to obtain initial fracture drawing pace of the interlayer and then schematic2D figure after the interlayer has happened initial instability can be designed based on these drawing paces calculated above.According to this schematic2D figure, the designed shape can be proved reasonably by the long term stability of this gas storage during the operation period.(2)Stability evaluation of the interlayer after initial fracture can be established by the combination of displacement cusp catastrophe theory and stability evaluation law about strength reduction of finite element method (FEM), and then the stability safety factor (SSF) can be obtained. Moreover, the influences of the depth of this interlayer, internal pressure, and solution time on the stability of interlayer are discussed respectively.