Mathematic modelling of the debrining for a salt cavern gas storage

Debrining is one of the key steps to complete the construction of a salt cavern gas storage, which determines whether the cavern can transfer to underground gas storage (UGS) and the effective volume of a salt cavern UGS. A mathematical model is proposed based on the change characteristic of the dynamic depth of the interface between gas and brine and the pressure equilibrium principle to predict the parameters of the debrining. The calculating equations of debrining parameters, such as, total debrining time, gas injection pressure, gas injection volume per day, and cumulative gas injection volume, are deduced. A calculating program is developed based on the deduced equations by using Visual Basic computer language. To verify the proposed mathematical model, MZ-1 cavern of Jintan salt district, Jiangsu province, China, is simulated as an example. Based on the calculating results, the debrining parameters of MZ-1 cavern are optimized. These parameters were used in the debrining of MZ-1 cavern. By comparing the analytical results with field monitoring data, the proposed mathematical model is shown to have a high accuracy. The error between the predicting results and the field monitoring data is less than 5%, which can satisfy the requirement of actual debrining prediction. Research results can provide the parameter optimization and prediction for the debrining of salt caverns used for gas storage in Jintan salt district and some other places with similar conditions.