Practical 3D-Connected Atomistic Kerogen Models over a Large Maturity Range

Most of the existing atomistic kerogen models are made, by design, as assemblies of arbitrarily sized macromolecules, which question their ability to capture some of the intrinsic properties of the materials, like their stiffness, or their ability to sustain porosity under pressure. In contrast to these “molecular” models, here we describe in detail the properties of a database of 26 kerogen models made by simulating the natural evolution of type I and type III organic matter, from immature states up to far in the metagenesis stage, and for which the properties of the carbon skeleton, including stiffness and porosity, emerge from the simulations, without any a priori assumptions. The chemistry of these models is corrected with a simple algorithm, removing all possible radical sites, cumulene and triple bonds, to make them useable for extensive simulations with a suitable molecular mechanics forcefield, or for electronic structure calculations, which is demonstrated by the calculation of infrared spectra using density-functional tight binding molecular dynamics. The proposed forcefield is adapted for simulations of fluid adsorption or transport in a flexible kerogen framework, which accounts for any type of kerogen deformation, including for instance adsorption-induced deformations. All the models, including the forcefield parameters, are freely available for download.