Natural gas production from shale in recent years has made a significant impact on the energy sector. It also presents potential opportunities to mitigate global warming by using shale reservoirs for CO2 sequestration. We attempt to understand the microscopic impact of shale on CO2 transport. We utilize equilibrium molecular dynamics (MD) to study the diffusion behavior of CO2 in the clay part of shales. Such microscopic examination can connect micro-scale calculations to macro-scale measurements. Results show that confinement has profound effects on CO2 diffusion. The diffusion coefficient was found to be slightly anisotropic due to the nature of the clay surface. (C) 2017 Elsevier B.V. All rights reserved.