Near Wellbore Challenges to Hydrogen Sequestration in Depleted Oil and Gas Reservoirs

Summary Underground hydrogen storage in depleted oil and gas reservoirs is gaining interest as a clean energy storage solution but presents notable technical challenges due to hydrogen’s small molecular size and high reactivity. These characteristics raise concerns about safe containment in subsurface environments, particularly with respect to well casing and cement integrity. Hydrogen can cause metallic embrittlement, corrosion, and stress-related fatigue in tubulars, while its diffusivity can lead to leakages and isolation failures. Similarly, cement layers may suffer from increased porosity, chemical degradation, poor bonding, and reduced mechanical strength, all of which jeopardize long-term well integrity. To assess risk, wells are classified into four types based on their usage and project context: Type 1 (old wells in new projects) face the highest risk, followed by Type 4 (existing wells in ongoing projects). Type 2 and Type 3 (new wells) pose the lowest risk due to better design and material selection. A severity framework ranging from low to severe helps evaluate integrity issues. While underground hydrogen storage is feasible, it requires careful assessment and mitigation of these risks to ensure operational safety and containment reliability, leveraging knowledge from past CO2 storage projects.