Wettability in the methane (CH4)–liquid–rock system is a key parameter which determines gas recovery and geo-storage efficiencies. However, there is a lack of an overview over this area; thus, we critically review this parameter from experimental and theoretical perspectives and discuss the impact of pressure and temperature conditions, fluid properties (salinity, ion type, and aqueous versus nonaqueous) as well as rock surface chemistry and roughness. Current research gaps are identified, a future outlook is provided, and several conclusions are reached. Therefore, this mini review improves fundamental understanding of wettability in the CH4–liquid–rock system at in situ reservoir conditions and provides useful guidance on the areas of shale gas/coalbed methane recovery and natural gas geo-storage.

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Liquid permeability is a key petrophysical parameter that quantifies the ability of a liquid to flow through porous rock/ soil and can be used in determining the efficiency of many subsurface processes, including enhanced hydrocarbon recovery, groundwater transport, carbon dioxide geostorage, underground hydrogen storage, etc. However, it is time-consuming (usually >16−240 h) and challenging to measure the liquid permeability for tight/shale rocks, particularly when the permeability is 100 nD or lower. The objective of this study is to develop a rapid and simple approach to determine liquid (brine or oil) permeability in tight siltstones/shales. Specifically, the developed method is based on the combination of one-dimensional (1D) vacuum imbibition experiments in tight/shale core plugs and a modified Lucas− Washburn model. For our proof-of-concept study, the results have demonstrated that (1) only 44−116 h are required to determine the liquid permeability (98−608 nD) for the analyzed samples from the Montney and Yanchang Formations; and (2) the acquired brine permeability was 28.3−28.5% lower than the slip-corrected nitrogen (N 2 ) permeability derived from the pulse-decay permeability tests. This is the first attempt to determine the absolute permeability of a liquid according to a 1D vacuum imbibition experiment and theory. This study provides a promising technique for the fast characterization of ultratight formation permeability of around 100 nD.

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