This thesis addresses the critical challenge of secure and efficient underground hydrogen storage (UHS), a key component in the global transition to clean energy and the achievement of carbon neutrality goals under the Paris Agreement. Hydrogen, as a zero-emission energy carrier, holds vast potential across multiple sectors; however, its small molecular size and high diffusivity pose significant leakage risks during storage. Ensuring the integrity of caprocks that seal underground reservoirs is therefore essential. The core focus of this research is the assessment of experimental methods dedicated to evaluating caprock sealing efficiency through representative measurement of capillary threshold pressure a fundamental parameter that determines a caprock’s hydraulic ability to prevent hydrogen migration.