Free Volume Model for Transport in Flexible Kerogen of Source Rock's Organic Matter.

Area of Science:

• Geochemistry
• Materials Science
• Chemical Engineering

Background:

• Kerogen, a complex organic matter in sedimentary rocks, possesses a microporous structure crucial for hydrocarbon storage.
• Understanding fluid transport within kerogen is vital for accurately modeling oil and gas recovery.
• Kerogen's flexibility and adsorption-induced swelling significantly influence fluid behavior within its pores.

Purpose of the Study:

• To develop a predictive model for adsorbed fluid transport in flexible kerogen.
• To investigate the impact of kerogen flexibility and swelling on fluid diffusion.
• To establish a relationship between fluid loading, self-diffusion coefficients, and free volume.

Main Methods:

• Utilized Fujita-Kishimoto free volume theory, originally developed for swellable polymers.
• Employed molecular dynamics calculations to obtain self-diffusion coefficients for a representative kerogen model.
• Analyzed the coupling between fluid molecule dynamics and kerogen matrix atom dynamics.

Main Results:

• Transport within flexible kerogen shows no significant collective effects in the long-time limit.
• Averaging over anisotropic diffusion properties is feasible for modeling transport behavior with fluid loading.
• A direct correlation was established between increased self-diffusion coefficients, accessible free volume, and fluid loading via the Fujita-Kishimoto model.

Conclusions:

• The developed model effectively links fluid transport properties to kerogen swelling and fluid loading.
• Model parameters provide insights into the evolution of transport behavior under varying thermophysical conditions.
• This work enhances the understanding of fluid dynamics in complex kerogen systems.