  Carbon capture and storage (CCS) technology has been applied successfully in
recent decades to reduce carbon emissions and alleviate global warming. In this
regard, shale reservoirs present tremendous potential for carbon dioxide (CO2)
sequestration as they have a large number of nanopores. Molecular dynamics (MD)
and MD-Monte Carlo (MDMC) methods were employed in this work to study the
absorption behavior of CO2 in shale organic porous media. The MDMC method is
used to analyze the spatial states of CO2, and the results are in good
agreement with MD results, and it also performs well in the acceleration
compared to the classical MD. With regard to the kerogen matrix, its
properties, such as the pore size distribution (PSD), pore volume, and surface
area, are determined to describe its different compression states and the
effects of CO2 absorption on it. The potential energy distribution and
potential of mean force are analyzed to verify the spatial distribution of CO2
molecules. The heterogeneity of the pore structure resulted in heterogeneous
distributions of CO2 molecules in kerogen porous media. Moreover, strong
compression of the matrix reduces the number of large pores, and the PSD is
mainly between 0 and 15 Angstrom. Despite the high interaction force of the
kerogen matrix, the high-potential-energy region induced by the kerogen
skeleton also contributes to the formation of low-energy regions that encourage
the entry of CO2. An increase in temperature facilitates the absorption
process, allowing CO2 molecules to enter the isolated pores with stronger
thermal motion, thereby increasing the storage capacity for CO2. However, the
development of geothermal energy may not be suitable for CO2 sequestration.
