Experimental Investigation of Integrity Issues of UGS Containing Hydrogen

Abstract Hydrogen is portrayed as the fuel of the future. The storage of hydrogen in porous underground gas storages is a promising solution for large-scale energy storage in Germany. In theory, excess energy sourced from renewable sources would be converted to hydrogen and subsequently stored in underground porous media. This solution provides cost effective solutions whilst providing large capacities in comparison to other energy storage types, however hydrogen interactions in underground gas storage sites (UGS) is a perplexing topic due to its foreign nature and therefore its behavior in the subsurface could be unpredictable. The implementation of autoclaves to recreate UGS with added hydrogen is a novel approach to investigate potential integrity issues that may arise during its lifetime. Where autoclaves can simulate conditions similar to UGS to analyze potential changes in the subsurface. The principal idea of autoclaves are to house samples which are exposed to pressures and temperatures equivalent that of typical Underground Gas Storages (max 200 bar, 120°C), allowing the recreation of any reservoir environment. The Primary objective is to investigate interactions between subsurface materials combined with reservoir rock and hydrogen. Aforementioned interactions can be interpreted through the analysis of mineralogical, petrophysical, hydrochemical changes to ascertain information regarding to the productivity of the UGS, for examples reviewing changes in permeability and porosity. Furthermore, the application of autoclaves can help to estimate the magnitude of hydrogen damage in subsurface equipment by providing insight into identifying key materials necessary to design a system preventing hydrogen damage to the subsurface; Supplementary implementation of conventional component inspection of mechanical properties of steels and cements through tensile strength testing and unconfined compressive strength testing, respectively, enable the extent of hydrogen damage inspection in UGS with added hydrogen. Predominantly API grade steels and API Grade G cement where used for this investigation. Preliminary autoclave experimentation results show that hydrogen can alter the characteristics of UGS, where API steels have shown to experience mild hydrogen damage and reservoir rock and API cement G samples have alterations in their chemical and physical characteristics. Autoclaves provide flexible choice in testing parameters and can be used to recreate any UGS with any gas mixtures, allowing for limitless testing possibilities to test for potential integrity issues in porous UGS containing hydrogen.