ABSTRACT:

As an important supporting project of the “West-to-East Gas Pipeline project” of China, the construction of the underground gas storage (UGS) of salt cavern in Jintan is mainly to solve the problem of emergency gas supply. Due to the unbalanced gas supply caused by seasons, climate changes and the accidental failure of gas transmission pipeline. In this paper, the construction and operation stability of gas storage in layered salt rock are employed as the research topics. The optimal gas injection and extraction operation schemes are determined by studying the operating characteristics of the salt cavern gas storage. Based on the geological conditions of the Jintan gas storage and the measured data of sonar, a set of theoretical methods is used to determine the operating pressure interval. The finite-difference software FLAC3D was used to simulate the entire process of four gas injection and extraction scheme. The entire operation process can be divided into four stages: constant high pressure stage, step-down gas extraction stage, constant low pressure stage, and pressurized gas injection stage. The volume shrinkage, key point displacement, cavity deformation and plastic zone distribution are discussed and analyzed in a numerical way. The results show that the unstable gas extraction/injection rate and frequent gas injection/extraction are not conducive to the stability of UGS. By comparing with the simulated results of the constant average internal pressure, it is shown that the changes of gas storage during the gas injection/extraction phase can be roughly estimated based on the average internal pressure monitored at the site. The research results can provide reference for the design of UGS operation scheme and the later operation management.

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