关键词: 盐穴储氢, 高频注采, 层状盐岩, 密闭性分析

Abstract:

Hydrogen energy storage plays a crucial role in balancing the load of renewable energy sources. Owing to the intermittent and volatile nature of wind and solar energy, combined with the variability in hydrogen storage, salt cavern hydrogen storage usually covers a wide range of injection and production frequencies. These cycles can span weeks, months, quarters, or even years. This is a unique feature of hydrogen storage in salt caverns. However, the impact of varying frequencies on the tightness of salt cavern storage remains unclear and requires further investigation. This study aims to evaluate the effects of injection and production frequency, internal pressure of hydrogen storage, and burial depth on the tightness of salt caverns under high-frequency operational conditions. To achieve this, a two-cavity three-dimensional model of a salt cavern was established and simulated using FLAC3D.The key outputs include the hydrogen seepage range, interlayer pore pressure variation, and cumulated hydrogen leakage rate after 30 years of operation under various conditions. Based on this, the influence of various factors on the tightness of salt cavern is analyzed. The results show that the cumulative leakage of hydrogen increases as injection and production frequency rise. As the injection and production frequency increase, the interlayer pore pressure near the salt cavern area near the salt cavern decreases, while the interlayer pore pressure farther from the salt cavern rises. At the same frequency, hydrogen leakage rates also increase with greater burial depths. Furthermore, higher injection and production frequencies result in a lower minimum operating pressure for the salt cavern, which leads to increased hydrogen leakage. Interlayer permeability significantly impacts the air tightness of the salt cavern, with interlayer hydrogen leakage accounting for more than 90% of the total leakage. When salt cavern is used for hydrogen storage, the interlayer permeability should be less than 1.0×10^-18 m².

Key words: salt caverns hydrogen storage, high frequency injection-production, bedded salt rock, tightness evaluation