Interfacial wettability evolution in underground hydrogen storage: Key factors, multiscale effects, and challenges.

Area of Science:

• Geochemistry
• Petroleum Engineering
• Material Science

Background:

• Underground hydrogen storage (UHS) is vital for managing hydrogen demand fluctuations.
• Wettability at the hydrogen-fluid-rock interface critically impacts storage capacity and recovery efficiency.

Purpose of the Study:

• To systematically review the evolution of multiphase interfacial wettability during UHS.
• To identify key factors influencing wettability and their multiscale impacts on storage.

Main Methods:

• Systematic literature review of wettability evolution in UHS.
• Discussion of characterization techniques, including 4D X-ray microscopy for in-situ dynamic analysis.
• Analysis of influencing factors: geological media, gas composition, salinity, temperature, pressure, microorganisms, and organic acids.

Main Results:

• Wettability is governed by multiple factors, with limited research on their coupled effects.
• Nanofluids show potential for wettability control.
• Wettability evolution impacts adsorption, saturation, gas column height, and relative permeability modeling.

Conclusions:

• Accurate macro-scale simulation of UHS requires incorporating mixed wettability into relative permeability hysteresis models.
• Fundamental insights into wettability evolution can enhance UHS safety and efficiency.