A NOVEL HYBRID NANO-CONTINUUM MODELING FRAMEWORK FOR THE TRANSPORT PROCESSES IN KEROGEN

The knowledge gap in understanding hydrocarbon transport in organic-rich shale rocks is primarily due to the presence of extensive nanometer-scale pores and their complex spatial connectivity. Among all the constituents in organic-rich shale rock, the organic matter (also called “kerogen”) possesses pore spaces across a wide range of scales from sub-nanometer to micrometers and plays a central role in controlling hydrocarbon transport in shale rock. To date, no unified physics-based models are yet available to fully describe the hydrocarbon transport processes in the multiscale pore domains of kerogen. In the present work, we combine hyper-resolution imaging techniques (i.e., Helium ion microscope imaging) and image-based modeling to develop a novel hybrid nano-continuum modeling framework for the transport processes in kerogen. The hybrid framework treats the smaller pores (i.e., pores below the image resolution) from sub-nanometer to a few nanometers as a continuum using models derived from molecular simulations based on realistic kerogen’s nanostructures, while explicitly representing the transport processes in the larger pores from tens to hundreds of nanometers and beyond (i.e., pores that resolved in the images) using a pore network model accounting for the deviation from Stokes flow across a wide range of Knudsen number. The results show that adsorption-desorption processes at the pore walls mainly control the fluid behavior in smaller pores while the transport of free-state gas in supercritical phase reflect the fluid behavior in larger pores. These processes are strongly regulated by the complex spatial arrangement of the multiscale pore domains. Our modeling framework provides a fully physics-based model for the transport processes in kerogen, which allows us to derive upscaled models that can be used for field-scale simulation of hydrocarbon production from unconventional shale formations.