Study On Stability Law Of Surrounding Rock During Operation Of Salt Cavern Gas Storage

Salt rock is suitable for underground gas storage due to its low permeability,damage repair and creep.Unlike foreign halite,gypsum domestic main continental sedimentary evaporation for special material,due to its halite layers,thin thickness of single layer and the characteristics of intercalation more exist in salt rock,the formation mechanics parameters and constitutive model is difficult to directly use the foreign research results is analyzed,and the domestic for the safe operation of the salt cavity gas storage,More attention needs to be paid to its stability and safety.Therefore,it is of great significance to study the stability of surrounding rock of gas storage with interlayer in operation.In this paper,the mechanical properties of salt rock and the stability of surrounding rock of salt cavern gas storage are studied by theoretical analysis,experimental study and numerical simulation.Based on the investigation of domestic and foreign literatures,the mechanical constitutive model of salt rock and the evaluation criteria of surrounding rock stability of salt cavern gas storage are summarized,which lays a foundation for the subsequent experimental and numerical simulation research.According to the salt rock samples provided by a basin and the mud content of the measured rock samples,the salt rocks are divided into the ones with high purity,certain mud content and high mud content.Respectively for three kinds of sample single triaxial compressive strength test,the tensile strength and creep experiments research,through the analysis of characteristics of rock damage and the experimental data,the processing of power law model is chosen as the salt cavity gas storage in the creep constitutive model of gypsum,determining the compressive strength of all kinds of gypsum,tensile strength,elastic modulus,poisson’s ratio,cohesive force,internal friction Angle and creep parameters.Based on FLAC 3d finite difference software,3D model including laminated salt cavity gas storage,the different operating pressure in the cavity,cavity to change shape,interlining position,quantity,and the thickness of the simulation results,based on cavity weeks displacement and stress analysis calculation with laminated salt cavity gas storage operation in 20 years,the wall,roof and floor deformation,shrinkage cavity volume,Tensile stress failure,expansion damage and gas puncture risk.The results show that the operating pressure of the gas storage is 6MPa～18MPa,the best cavity shape is spherical,the interlayer is located in the middle of the cavity,and the less the number of interlayers and the smaller the thickness of the interlayer,the better the stability of the surrounding rock of the salt cavern gas storage.The regularity knowledge obtained in this paper is expected to provide some reference for the field construction and operation of salt cavern gas storage with interlayer.