Experimental investigation on the crystallization mechanism and mitigation strategies for gas injection and brine discharge pipes in salt caverns

Abstract

Salt cavern gas storage (SCGS) not only holds promise for CO2 storage but also helps combat climate change by providing a reliable and adaptable solution for storing natural gas. Herein, this capability facilitates the integration of renewable energy sources and helps decrease greenhouse gas emissions from fossil fuel-based power generation. Firstly, a physical simulation platform for gas injection and brine discharge was developed to investigate the crystallization mechanism and devise preventive measures for constructing SCGS. Secondly, the study involved analyzing the mechanism of brine crystallization and determining experimental parameters using similarity theory. Furthermore, the effects of gas/water injection temperature, brine temperature in the salt cavern, flow rate, and pipe wall roughness on brine crystallization were examined. Finally, preventive measures were suggested to address issues related to crystallization and blockage. Results indicate that a 10℃ increase in gas/ water injection temperature leads to an average decrease of 26.56 % in the crystallization rate, while a corresponding increase of 186.16 % occurs for brine temperature. Heating the injected gas/water and opting for shallow strata for SCGS construction can alleviate crystallization. The crystallization rate initially increases and then decreases with flow rate, with a preferable flow rate exceeding 96 m3/h to prevent crystal adhesion and enhance scouring effects. Therefore, crystallization in the middle of the brine discharge pipe warrants special attention. Significantly reducing pipe wall roughness can effec- tively minimize crystallization, highlighting the importance of developing erosion-resistant coatings. Moreover, a proposed small U-shaped pipe backflushing method aims to solve blockages, along with preliminary application suggestions.