Molecular Simulation of Bulk Organic Matter in Type II Shales in the Middle of the Oil Formation Window

Abstract

In this work, we use molecular simulations to determine the structural and physical properties of the organic matter present in type II shales in the middle of the oil generation window. The construction of molecular models of organic matter constrained by experimental data is discussed. Using a realistic molecular model of organic matter, we generate, by molecular dynamics simulations, structures that mimic bulk organic matter under typical reservoir conditions. Consistent results on density, diffusion, and specific adsorption are found between simulated and experimental data. These structures enable us to provide information on the fluid distribution within the organic matter, the pore size distributions, the isothermal compressibility, and the dynamic of the fluids within the kerogen matrix. This study shows that a consistent description at the molecular level combined with molecular simulations can be useful, in complement of experiments, to investigate the organic matter present in shales.

Fast mass transport of oil and supercritical carbon dioxide through organic nanopores in shale

“…11. It is evident that the pore diameter of the kerogen sample spans from a few Å to $14 Å, consistent with the simulation results reported by Collell et al [68]. To estimate the diffusion coefficient of n-octane through the disordered kerogen, we used grand canonical Monte Carlo (GCMC) simulations to generate initial structure of MD simulations.…”

“…Recent molecular simulation shows that kerogen density, specific adsorption, and other properties estimated from their model are consistent with the experimental data [68]. Here, we focus on the type II-C kerogen unit (Fig.…”

“…As suggested by the developer of the kerogen model, we used all-atom pcff + force field to describe the interatomic potentials [67,68]. The LJ interactions between different species were determined through the Waldman-Hagler combining rules and the terms beyond the cutoff distance of 9.5 Å were also included via long-range tail correction.…”

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

“…At the same time, using the Extended Langmuir model and Ideal Adsorbed Solution (IAS) model to fit the experimental results, Collell found that the predicted results of the two models were consistent with the simulation results under low pressure conditions, but at high pressure, only a small part of the predicted results was in agreement with the simulation results, and the smaller the pores, the worse the match between the properties became [47]. In the same year, based on the experimental data, Collell used the molecular simulation method to obtain the molecular structure and the physical properties of shale organics and obtained the stable kerogen molecular structure by molecular dynamics simulation [48]. Based on the C/H and C/O ration of I, II and III kerogen, Ungerer et al applied a molecular simulation method to establish a molecular structure model.…”

Novel molecular simulation process design of adsorption in realistic shale kerogen spherical pores

“…Zhang and LeBoeuf constructed molecules for Green River Shale kerogen and calculated the density and thermal expansion coefficient by MD [37]. Collell et al provided new models for type II kerogen and analyzed the micropore structure for the solid [9]. Bousige et al proposed a general kerogen molecule reconstruction method based on the carbon-carbon pair distribution function for all types of kerogen [5].…”