In addition to the continued development and refinement of shale hydraulic fracturing technology, shale gas production is commercially viable and could meet future energy and economic demands. However, the gas–water coexistence environment within shale reservoirs significantly weakens shale’s adsorption capacity. Therefore, accurately describing gas’s adsorption behavior under the influence of water has become a critical research topic for the evaluation and development of unconventional reservoirs. In this study, the role of water in nanoconfined spaces was examined first. By modifying the molar’s volume, the Soave–Redlich–Kwong equation of state (SRK-EOS) was improved. That approach quantitatively characterized a fluid’s adsorption behavior within shale’s nanoconfined spaces and critical property’s changes. Second, the modified SRK-EOS combined with the (3/8) σff condition was integrated into an SLD structure and validated by using published methane isothermal adsorption test data from dry and water-saturated shales. The results indicated that the model agrees well with the experimental data, effectively characterizing confined gas’s adsorption behavior in dry and water-saturated shale. Water occupies effective adsorption space within pores, compressing pore volume and further amplifying shifts in gas’s critical properties, while reducing shale gas’s adsorption capacity. Additionally, gases tend to exist in bulk rather than in the adsorbed phase as the temperature rises, and the density of the adsorbed phase decreases. These results have significant implications for advancing our knowledge of the mechanisms underlying the accumulation of shale gas, thus enhancing production forecasting.
Chen et al. (Fri,) studied this question.