The engineering thermal analysis for natural gas storage in deep salt formation

Engineering thermal analysis for natural gas storage in deep salt formation is one of the bases of stability evaluation and running control. The presented analysis, in which the actual cavern shape and the thermal field were considered, is based on the variable mass system thermodynamics and it is performed on the FLAC(3D). The numerical analysis results show that: the pressures of wellbore top and gas (in cavern) increase linearly during injection process and decrease linearly during production process; the change of temperature of gas and cavern wall obey parabola law during injection process; during production process, the temperature decreases firstly, then the decrease tendency slows down, and the temperature even increases a few at last; the temperature of wellbore bottom and top changes as that of gas does during the whole cycle but the former change magnitude is smaller than the later one. Though the influence range of temperature field during the performance is only 7-15 m around the cavern, the temperature gradient is very greater comparatively. This high gradient of temperature may affect the stability of the cavern.