Coupling Simulation of Drilling Behavior in Cavity Bottom Sediments of Salt Cavern Gas Storage

In terrestrial salt cavern gas storage facilities in regions such as Jintan, China, the development of mud interlayers in the formation causes sediment to accumulate at the bottom of the cavern after water-based dissolution, occupying nearly half of the effective storage capacity. To revitalize the void resources of sediment and optimize the rotary jetting drilling process at the cavern bottom, a CFD-DEM two-way coupled numerical simulation method was adopted. By considering both continuous flow of the drilling fluid and the discrete mechanical characteristics of the sediment particles, a numerical simulation study on rotary jetting drilling within the unlithified sediment of salt cavern was. The results show that: Through the coupled numerical simulation, the full-process dynamic characteristics of sediment particle mobilization, migration, and accumulation during the rotaryting drilling within the sediment can be reproduced, and the influence of different drilling flow rates on the sediment fragmentation efficiency and particle upward migration rate can be quantitatively analyzed. Flow rate and the structure of the drilling tool significantly affect the hole-forming effect of rotary jetting drilling within the sediment. Increasing the flow rate can enlarge the hole and depth, but the increase in drilling efficiency slows down after exceeding a critical value. At the same flow rate, the drilling tool with a small-diameter nozzle exhibits drilling efficiency within the sediment, and the nozzle diameter has a negligible effect on the hole-forming area. The drilling tool configured with a 5- guide impeller and3 rear-mounted reverse nozzles achieves the optimal drilling performance, and different nozzle structures correspond to exclusive optimal construction flow rate intervals. The research findings can provide a theoretical basis for the selection of drilling tools for salt cavity sludge, optimization of construction parameters, and the resource utilization of sludge in salt cavern gas storage facilities in regions such as Jintan.