Hydrogen seepage mechanism in surrounding wall of underground salt caverns, a numerical study in microscopic system

In this paper, we present a microscopic numerical system for simulating the hydrogen seepage in surrounding walls of underground salt caverns, used for potential hydrogen storage in large scale geological storage. Klinkenberg effect is considered for hydrogen flow in low-permeability rock salt formation. A DEM-CFD coupled method is implemented to characterize the seepage behavior of hydrogen. Finite Volume Method is employed to solve coupled partial differential equation (PDE) for seepage field. The methodology is presented in a flowchart. Numerical simulations were conducted to obtain pore pressure variations, gas velocity field distributions, and particle displacement under multiple operating conditions. Taking advantage of DEM, the simulation results indicate the direction of hydrogen seepage is partially aligned with the initial pressure gradient and partially flows from the mudstone layer into the rock salt layer. Hydrogen seepage between rock salt and interlayers leads to pronounced particle deformation at the interface of the interlayer, which may become potential risk spots for hydrogen leakage. The results of this research reveal characteristics of hydrogen leakage during operation that may help us understanding hydrogen seepage mechanism at microscopic level.