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Molecular Modeling of Kerogen Structure, Thermodynamic, and Transport Properties

Optimize experimentation with Molecular Dynamic, #NEMD, and #GCMC

Understanding the properties of kerogen is necessary for a better assessment of #shale gas and shale oil extraction prospects. It is also essential to understand the physics of in-situ oil shale #retorting. Thanks to the availability of well-tested computational methods, molecular modeling can aid in directing and optimizing the value of costly and time-consuming experiments. This talk illustrates the capabilities of molecular modeling to predict important #thermodynamic properties of kerogen as well as the transport behavior of fluids through kerogen.

First, we created model kerogen structures for type I (Green River Shales) and atype II (marine origin shales) at various maturity levels. Using kerogen property data from the literature for H, O, N, and S concentrations, aromaticity, average chain length, the size distribution of polyaromatic units, and types of NSO-containing units, we built kerogen models of moderate size (200 to 500 carbon atoms).

These model structures were relaxed via molecular dynamics (MD), using successive NPT simulations at decreasing temperatures with the pcff+ forcefield. Final predicted densities agree  with reported experimental values for type I and type II kerogens and with known kerogen structural characteristics (e.g., spontaneous organization of polyaromatic units into parallel stacks). Thermal expansion coefficients and bulk elastic moduli can be deduced. Interestingly, some aspects of kerogen structures appear glassy, such as the location of polyaromatic nuclei changes very slowly, whereas others, such as local alkyl chain mobility, do not.

Finally, the interactions of kerogen with #fluids were investigated. MD simulations allow determination of thermodynamic properties (e.g., partial enthalpies, partial molar volume of fluids in the kerogen phase). Grand Canonical Monte Carlo (GCMC) analyses provide adsorption isotherms of gases like methane or ethane in the kerogen micropores under shale gas reservoir conditions. Diffusion of gas molecules through kerogen is modeled using non-equilibrium molecular dynamics (NEMD). Comparisons of initial computed properties with experimental data are encouraging, and ways of improving predictions are outlined in the conclusions.

#Kerogen #atomistic #simulation #ComputationalDesign #materialdesign #materialsengineering #oil #gas #oilandgas #materialscience #oilandgasindustry #materialscience #energy #GUI #GIBBS #Co2 #moleculardynamics #materialsscience #Sustainability #MaterialDesign #modelingandsimulation #MedeA #MedeAEnvironment #modeling #simulation #fuels #engineering #Simulation #modeling #gasoline #chemistry #naturalgas #crudeoil


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