Remediation technique for microbiological clogging in the water curtain system of underground LPG storage caverns

One of the greatest difficulties in operating the underground LPG storage cavern is either the prediction or the prevention of clogging phenomena, which is developed by microbes, occurred in the rock fractures around the water curtain system. As a result of monitoring data analysis, it was revealed that the bacteriological clogging area would range from the water curtain system to the area of storage caverns. A finite element numerical analysis program was developed to solve the one-dimensional advection-dispersion equation combined with Monod relation and to predict the transport distance and time of microbial clogging plume. Furthermore, remedial solution (NaOCl) was injected for the purpose of cleaning the clogged area, but the bacterial counts variation data showed that the sterilization of microbes seemed to be unsatisfactory. Numerical analysis was performed to find out the transport behavior of the remedial solution in the onground pipeline, water curtain system, and fractured rock media. The results of analysis showed that the NaOCl solution was diluted up to 35% of initial concentration at water curtain system, and approximately 95% of the diluted solution was transferred into the fractured rock around the water curtain system. It was, therefore, believed that the concentration of NaOCl in onground the reservoir tank must be maintained at least 50% higher concentration than present condition.