Shale, a heterogeneous and extremely complex gas reservoir, contains low porosity and ultra-Low permeability properties at different pore scales. Its flow behaviors are more complicated due to different forms of flow regimes under laboratory conditions. Flow regimes change with respect to pore scale variation resulting in change in gas permeability. This work presents new insights regarding the change of pore radius due to gas adsorption, effective stress and impact of both on shale gas permeability measurements in flow regimes. From this study, it was revealed that the value of Klinkenberg coefficient has been affected due to gas adsorption-induced pore radius thickness impacts and resulting change in gas permeability. The gas permeability measured from new proposed equation is provides better results as compare to existing equation. Adsorption parameters are the key factors that affect radius of shale pore. Both adsorption and effective stress have an effect on the pore radius and result gas permeability change. It was found that slip effect enhances the apparent gas permeability and also changes with effective stress; therefore, combine impact of slip flow and effective stress is very important as provides understanding in evolution of apparent permeability during shale gas production.

Measurement of gas sorption capacity in a shale gas reservoir is significant to comprehending the mechanism of gas storage and resource assessments. In this study, gas sorption experiments on shale samples have been conducted, and a gas sorption analytical model has been proposed. This model is validated with previously published data. With this, the effective porosity is analyzed by combining the gas sorption and stress equations, and the shale gas-in-place (GIP) is calculated using a previous and newly proposed method. The influence of porosity (adsorbed/sorbed) on shale GIP is also examined. The results show that the proposed model provides the adsorbed and absorbed gases' contribution in total gas storage capacity, and its results are better than the Langmuir model. Moreover, it is also determined that the effective porosity performs a key part in characterizing the shale gas reservoirs, and it decreases with the increase in pore pressure. The results also reveal that higher total gas storages are obtained due to gas absorption, at low pressure, using the new proposed method. Further, with the increase in pressure, the total gas storage capacity increases, according to the shale sample characteristics, i.e., absorption and adsorption. Furthermore, the total gas storage is also altered due to adsorbed/sorbed porosity. The amount of absorbed gas ranges from 18.99-19.45% and is observed in this study.