(147l) Modeling Kerogen Flexibility upon Gas Adsorption Using Osmotic Ensemble Simulations

Molecular dynamics, Monte Carlo, Density functional theory, and Machine learning.

Abstract:

The purpose of this study is to improve our understanding of the pore structure and
adsorption properties of kerogen, the organic fraction of shales. This knowledge is crucial for
predicting the gas storage capacities, as well as enhancing hydrocarbon recovery in shales.
We examine the chemical structure of kerogen units at varying levels of maturity and utilize
these units to create three-dimensional molecular models, which incorporate mesopores with
diverse size and shape within the microporous kerogen matrix. Next, we employ hybrid
MD/MC simulations of CH 4 adsorption in the osmotic thermodynamic ensemble. This
involves grand canonical MC simulations of gas adsorption in rigid structure followed by
MD simulations in the NPT ensemble to account for the matrix flexibility. The cycles are
repeated until a convergence in the number of particles and unit cell volume is achieved. The
proposed approach allows to determine to what extent the kerogen flexibility affects the
methane adsorption capacity in the wide range environmental conditions of shale reservoirs.
Work is supported by the NSF-CBET grant # 1834339.