Cathodic protection (CP) is one of the most effective methods of corrosion control for deep well casings. However, it is difficult to measure the casing-to-soil potential and to evaluate the effectiveness of CP in the field, due to the depth of well casings in excess of 3000m. Numerical simulation can be used to calculate the casing-to-soil potential along the well casing, as well as to determine the optimal parameters of CP systems according to the local environmental conditions. In this study, the numerical simulation is used on well casings for underground natural gas storage. Computer software with three-dimensional boundary element analysis capability is used for evaluating cathode protection performance of well casing. The effect of a cement layer on surface of the well casings is considered in the modeling progress. Furthermore, various parameters of the anode bed, such as the depth of anodes, the length of anodes and the distance between anodes and well casings are also studied to obtain the best protection performance. In addition, the comprehensive field measurements provide the detailed data about the soil that is considered as a multi-layered electrolyte with electric conductivity, which varies from one layer to another one. The aim of the simulation is to predict the level of protection potential along the well casings.
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