A Study on Petrophysical Modeling of Insoluble Sediments in Salt Caverns

Salt caverns are formed through water dissolution of salt rocks, serve as critical repositories for strategic energy reserves due to their excellent tightness. During the solution mining process, a substantial amount of unconsolidated, highly porous insoluble sediments accumulate at the bottom of salt caverns. These insoluble sediments can be transformed into viable underground spaces for gas storage following suitable engineering treatment. Existing petrophysical models of insoluble sediments are unable to accurately characterize these sediments. Based on the X-ray diffraction results of the sediment samples and the Voigt-Reuss-Hill model, this study determined the equivalent bulk and shear moduli of the solid phase particles, thereby establishing a matrix model for the sediments. A framework model was then constructed by incorporating the spherical particle model and the Hashin-Shtrikman bounds model, along with porosity parameters. Fluid substitution was performed on the sediment model using the Gassmann equation to obtain the saturated sediment model. The results demonstrate a agreement between the proposed model and the measured data, and they effectively reveal the response characteristics of the insoluble sediments under saturated brine conditions.