Status and development trend of solution mining technologies used for salt-cavern gas storage

As for salt-cavern gas storage, positive circulation dominated single well convection method is used for cavern building in China. The solution mining speed is low, and it takes 4-5 years to build a cavern of 20×10⁴ m³. It is difficult to meet the requirement on rapid development of underground gas storage (UGS) in China by using only a single solution mining method. Therefore, it is necessary to search for many solution mining methods suitable for UGS building in layered salt beds to increase solution mining speed. In this paper, the process and advantages & disadvantages of various solution mining modes were illustrated and analyzed based on numerical calculation and field application. And then, the causes to increase solution mining speed were analyzed on reverse-circulation, big-hole, twin-well and dual-string solution mining technologies. It is shown that the development trend of solution mining technologies for salt-cavern gas storage are mainly reverse-circulation, big-hole, twin-well and dual-string solution mining technologies, which can increase solution mining speed effectively. There are some disadvantages and difficulties in big-hole, twin-well and dual-string solution mining technologies and many key technologies shall be studied further. The difficulties of big-hole solution mining, twin-well solution mining and dual-string solution mining are well cementing, cavity control and detection, and brine corrosion to production casing, respectively. The reverse-circulation solution mining technology has been successfully applied in Jintan area. Cavity control and detection technologies are relatively mature, and solution mining speed can be increased by more than 20%. By virtue of this technology, domestic UGS building process is impelled effectively.