Equivalent Permeability Model for Sealing Evaluation of Natural Gas Storage Cavern in Bedded Rock Salt

An equivalent permeability model (EPM) is presented to calculate the equivalent permeability of non-salt layers, which makes the sealing evaluation of bedded salt cavern natural gas storage by numerical simulation easy and sufficient. In the numerical simulations, the effects of non-salt layer property parameters, i.e. horizontal permeability, vertical permeability and dip angle on the sealing of bedded salt cavern natural gas storage can be expressed by a single parameter, the equivalent permeability. We have studied the influence of non-salt dip angle, permeability anisotropy, permeability, buried depth, gas pressure, etc. on the time that it takes for the natural gas to migrate to the ground surface through the non-salt layer formation. The examples show that the EPM is precise and correct, and can meet the actual engineering demands, which includes fewer parameters, and it is implemented easily in numerical simulations. The time needed for natural gas to migrate to the surface is proportional to the increase in anisotropy of permeability and buried depth, but inversely proportional to the increase of non-salt layer dip angle, permeability and internal pressure. The permeability and the dip angle of non-salt layers are the key factors to be considered when analysing the sealing of bedded salt cavern natural gas storage.