Development of Atomistic Kerogen Models and Their Applications for Gas Adsorption and Diffusion: A Mini-Review

With the emergence of shale gas, numerous atomic-scale models of kerogen have been proposed in the literature. These models, which attempt to capture the structure, chemistry, and porosity of kerogens of various types and maturities, are nowadays commonly─if not routinely─used to gain nanoscale insights into the thermodynamics and dynamics of complex and important processes such as hydrocarbon recovery and carbon sequestration. However, modeling such a complex, disordered, and heterogeneous material is a particularly challenging task. It implies that important underlying assumptions and simplifications, which can significantly affect the predicted properties, have to be made when constructing the kerogen models. In this mini review, we discuss the existing atomistic models of kerogen by categorizing them according to the different approaches and assumptions used during their construction. For each type of model, we also describe how the construction strategy can impact the prediction of certain properties. Important work on kerogen interactions with gas and oil, from both the point of view of equilibrium adsorption (including adsorption-induced deformation) and transport, are described. Possible improvements and upscaling strategies─to better account for kerogen in its geological environment─are also discussed.