Brine-particle two-phase flow of the low-level debrining well in sediment-type salt cavern storage

Sediment-type salt cavern storage facilities are critical components of energy infrastructure that utilize the space within sediment voids to store gas. This is accomplished by injecting high-pressure natural gas or air into salt cavities, which displaces brine from the sediment voids. During the gas injection and brine displacement processes, the high-velocity flow of brine in low-level debrining wells carries sediment particles, leading to sand blockages that adversely affect brine expulsion efficiency. The forces acting on spherical particles during fall and horizontal movement were analyzed, resulting in the derivation of the terminal settling velocity formula for particles in free fall. Additionally, a terminal settling velocity formula that considers the morphologies of sediment particles and the sand concentration in brine was developed. Under identical conditions, brine with a higher sand concentration exhibits a greater capacity to carry sand. When the geometric mean diameter is constant, flatter-shaped particles are more readily transported by brine. Using a CFD-EDEM coupled simulation method, the distribution of the solid-liquid two-phase flow field in debrining wells was simulated over time, accounting for varying brine flow rates and sediment accumulation depths. When discharging brine at low flow rates, it is essential to promptly clear the debrining channel to prevent sediment accumulation at bends. The layering effect of brine flow rates results in particles in the lower section of the debrining channel accumulating more easily. At the same inlet flow rate, an increase in particle accumulation depth enhances the sand-carrying capacity of the brine. An analysis of the particle size distribution of returned sediment particles during the gas injection and brine displacement process in a specific salt cavern revealed a particle size range of 0.075 to 40 mm, which was consistent with the results obtained from simulation modeling. The primary sources of error and their corresponding solutions were also identified. The research findings provide valuable guidance for improving brine displacement efficiency and preventing sand entrainment and blockages in debrining wells associated with salt cavern void injection and brine displacement projects involving sediment-type salt caverns.