Study On Shape Control Techniques Of Cavities In Salt Formation For Underground Gas Storage

Cavities in salt formation for the purpose of natural gas storage are mainly builded through solution of salt. The salt will dissolve into the under saturated brine continuously while the fresh water injected into the cavity, and the cavity will enlarge step by step. In order to build a stable cavity for gas storage, the shape control techniques should be developed. Because of no any underground gas storage used in China, there is a little knowledge known about the shape control techniques until now, and the experimental equipment for the usage of this study is scare. The author of this paper aims to establish the shape control techniques by experimental study. Three sets of experimental equipment have been used for this purpose, which are: 1. Measurement for the dissolution rate of salt; 2. Study of diffusion and convection of injected fresh water into brine; 3. Shape control techniques of cavities. By means of experimental study, we can acquire the fundamental data, and master the mechanism of salt dissolution, and find out the shape control mechanism, and establish the shape control techniques. The pitoval factors affecting the shape of cavities include the pattern and position of the pad, the location of the tubing and casing, the circulation direction and the injection rate of fresh water. A steady state shape of a cavity can be got by optimize the variety of parameters at the appropriate time. The experimental tests show us that a steady cavity could be built by optimizing variety of parameters. The key factor controlling the shape of a cavity is the appropriate time to adjust the position of pad and pipes. The salt between the tubing and casing will dissolve more quickly when it exposed to the brine. We know well the factors affected the shape of cavities and the shape control techniques by means of experimental study, which could guide us to build a more stable cavity in salt formation for gas storage.