Technical Committee Underground Storage Technology

completion integrity

This project aims to help quantify the risk of storing hydrogen in underground storage facilities by specifically analyzing how the materials of a wellbore completion (cement and steel) behave in the presence of hydrogen at elevated pressures and temperatures. Hydrogen can cause problems when penetrating and staying trapped in different materials. In steels, the embrittlement effect is known, in which hydrogen penetrates the intercrystalline structure of steel in an atomic state, taking advantage of defects or by diffusing through the interstitial space, thus affecting its mechanical properties and opening space for its corrosion. On the other hand, to estimate the effect that hydrogen has on the cement, whose pores are initially saturated with reservoir water, it is necessary to estimate the capillary effect in contact with hydrogen within the pores. Pressurized hydrogen may diffuse through the formation water or entirely displace it, the latter meaning loss of integrity of the completion. The principal work package 2 contains testing on gas tightness in presence of water including the effect of capillary pressure due to which hydrogen is kept at a pressure above the hydrostatic pressure. Once the capillary pressure + hydrostatic pressure is exceeded, the formation water is displaced and free gas penetrates the pores. The magnitude of the capillary pressure effect is confirmed in work package 3 by measuring the governing system properties: interfacial tension and wetting angle. The findings on the governing mechanisms along with data on the diffusivity of hydrogen inside the pores that are filled with formation water are used to estimate the loss of hydrogen by help of simple correlations and numerical simulations.