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Hydrogen storage is essential in hydrogen value chains and subsurface storage may be the most suitable large-scale option. This paper reports numerical simulations of seasonal hydrogen storage in the Norne hydrocarbon field, offshore Norway. Three different storage schemes are examined by injecting pure hydrogen into the gas-, oil-, and water zones. Implementation of four annual withdrawal-injection cycles followed by one prolonged withdrawal period show that the thin gas zone is a preferred target with a final hydrogen recovery factor of 87%. The hydrogen distribution in the subsurface follow the geological structures and is restricted by fluid saturation and displacement efficiencies. Case studies show that the pre-injection of formation gas as a cushion gas efficiently increases the ultimate hydrogen recovery, but at the cost of hydrogen purity. The injection of 30% hydrogen-formation gas mixture results in a varying hydrogen fraction in the withdrawn gas. An alternative well placement down the dipping structure shows lower storage efficiency.

In this paper, we report the growth pattern and the rate of CH4 hydrate in sandstone pores. A high-pressure, water-wet, transparent micromodel with pores resembling a sandstone rock was used to visualize CH4 hydrate formation at reservoir conditions (P = 35–115 bar and T = 0.1–4.9 °C). The CH4 hydrate preferably formed and grew along the gas–water interface until the gas phase was completely encapsulated by a hydrate film. Two different growth rates were identified on the gas–water interface: CH4 hydrate film growth along the vertical pore walls (∼1200 μm/s) was more than 100 times faster than the film growth toward the pore center (∼8 μm/s). CH4 hydrate crystal growth directly in the water phase was slow and the rate was less than 0.5 μm/s. The film growth rate along the gas–water interface was independent of the pore size, gas saturation, and gas distribution, but the pore wall growth rate displayed a power law dependency on the applied subcooling temperature, ΔT, with a power law exponent equal to 2. The results of this study can be used as input to numerical models aiming to simulate pore-scale CH4 hydrate growth behavior. publishedVersion