The sudden massive extraction of shale hydrocarbons in the early 2000s has stimulated intense research efforts aimed at understanding the inner nature of kerogen, the microporous carbon entrapping most oil and gas. The maturity of kerogen - traducing its carbon content and aromaticity, which both depends on the nature of the precursor organic matter (OM) and burial history, significantly affect its stiffness, and hence, certainly as well the mechanism of fluid expulsion, even though such a correlation between chemistry, mechanics (or poromechanics) and transport has been poorly documented so far.<br/>Here we will first present an accelerated reactive molecular dynamics framework based on the replica exchange molecular dynamics method which as allowed us to simulate the geological burial of important type III (cellulose and lignin) and type II OM, up to kerogen and corresponding fluid (including oil and gas).<br/>In a second step, we will show how the generated kerogen models can be used to characterize the relationship between kerogen maturity and poromechanics, and especially the ability of the kerogen to swell or contract upon hydrocarbon adsorption/desorption, which can vary by one to two orders of magnitude depending on maturity.<br/>Finally, this will allows us to derive the laws governing the equilibrium and transport diffusivities of hydrocarbon within microporous kerogen and propose a purely microscopic origin for the well-known anomalous productivity decline.

From kerogen precursors to hydrocarbon expulsion: Insights from atomistic simulations

2019 Fall National Meeting

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