Construction prediction of horizontal energy storage salt caverns using a novel concentration-field model

Abstract

Horizontal salt caverns are widely used for oil and gas storage, hydrogen storage, compressed air energy storage, and carbon dioxide geological storage in bedded salt. Accurate modeling of solution mining processes is critical for predicting and controlling the shape and capacity of the caverns. To improve the accuracy and efficiency of such predictions, a novel construction prediction model is proposed using a simplified concentration field distribution model. The dissolution of salt and the convection of brine are simulated by solving the Navier-Stokes equations and the convective diffusion equation. Simulation results indicate that the injected freshwater mixes with the brine and forms an upward buoyant jet. Except in the buoyant jet region, there is a vertical concentration stratification. The brine concentration is the lowest from the apex of the buoyant jet to the cavern top, and gradually increases in the downward direction until the saturated zone below the injection port. In this regard, the simplified concentration field distribution model introduces a distribution factor β to describe these distribution patterns. A C++ simulation program, named “Horizontal Salt Cavern Construction Prediction”, is developed combining the simplified concentration model, the dissolution model and the grid system based on the Volume of Fluid Method. The construction of Volgograd Gas Storage is simulated for verification. Simulated brine concentration and cavern shapes coincide well with the actual cases, indicating that the proposed model is reliable. Work in this paper can serve as a new construction design tool and facilitate renewable energy storage in salt caverns.