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Significant quantities of gas are adsorbed onto the rock matrix in shale gas reservoirs. Accounting for this adsorbed gas in reservoir calculations is key for realistic estimations of gas in place, overall gas production and later as a target for enhanced gas recovery methods like thermal stimulation. Classical Langmuir isotherm fails to represent gas adsorption at multiple temperatures thereby making its application in thermal stimulation strategies limited. In this work, several temperature-dependent gas adsorption models were reviewed and grouped further into both temperature dependent and independent Langmuir volume. Application of the models to several shale gas data sets obtained from different regions show minimal differences in the successful prediction of gas adsorption using either the temperature dependent or independent Langmuir volume models. However, caution is to be exercised in the choice of

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CO 2 molecular diffusion in subsurface porous media is one of the key mechanisms in high-pressure−high-temperature CO 2 geosequestration and CO 2 -based enhanced oil recovery projects. The mass transfer rate of injected supercritical CO 2 and its dissolution in reservoir fluids are mainly described by the gas diffusion coefficient. Over the past decades, numerous efforts have been made to investigate the CO 2 molecular diffusion process in both hydrocarbon reservoirs and saline aquifers. However, various experimental methods and mathematical models with simplified assumptions were used to determine the CO 2 diffusivity, which sometimes led to inaccurate or contradicting results. Hence, it is essential to critically review and compare the CO 2 -diffusion-related literature for better application in geoscience, chemical, and petroleum engineering fields. In this review, we critically review the physics of CO 2 diffusion in porous and nanoporous media, including the diffusion theory, factors affecting the CO 2 diffusion coefficient in hydrocarbon reservoirs and saline aquifers, analysis of laboratory measurement methods, their advantages and disadvantages and limitations, and also evaluation of previously developed mathematical models and their uncertainties and empirical correlations, in detail. Additionally, we briefly discuss CO 2 dispersion in porous media from various aspects. Finally, potential research areas related to CO 2 diffusion in porous media are proposed.

Hydrogen has only been recently recognized as a hydrate former, forming structure II hydrate (sII). In this communication, we report new experimental hydrate stability data for the binary hydrogen + water system at pressures ranging from (111.4 to 178.4) MPa and temperature down to 264.45 K. In addition, the formation and dissociation of so-called semiclathrates of hydrogen in the presence of tetrabutylammonium bromide (TBAB) were evaluated. The clathrate and semiclathrate dissociation measurements were conducted using a standard constant volume (isochoric) technique together with step-heating for achieving equilibrium conditions.