Prediction method for calculating the porosity of insoluble sediments for salt cavern gas storage applications

Many insoluble sediments accumulate at cavern bottoms during the construction of salt caverns located in highly insoluble salt formations. Before using the void space for gas storage, knowing the porosity is essential for predicting void volume of insoluble sediments. However, most previous studies have focused on construction and operation of salt caverns, and insoluble sediments have been largely ignored. In this study, a series of laboratory tests, including screening and porosity tests, are conducted to obtain the particle size distribution and porosity of samples obtained by dissolving the nonsalt interlayers of target cavern. The results show that the porosity values of the samples decreases with increasing of fractal dimensions and have no relation to the maximum particle size when the fractal dimension is constant. Based on these results, a porosity prediction method is proposed to calculate the porosity of insoluble sediments combined with fractal and packing theories. In this method, the fractal dimension and the compaction index should be controlled within a reasonable range. The accuracy and reliability of this model was studied by calculating the porosity of insoluble sediments in an actual salt cavern. This study can provide a reference for evaluating the void volume in insoluble sediments.