Rough Surface Effect on CO₂ Displacement at the Nanoscale

CO2 injection has great potential for enhancingshaleoil recovery. Understanding the CO2 displacement in nanometerpores of shale is critical for developing effective CO2 injection techniques. In this work, we applied direct numericalsimulation to study the effect of the rough surface on CO2 displacement in nanometer pores of shale. By quantifying CO2 displacement in rough nanochannels, we aimed to understandhow surface roughness and morphology affect displacement progress.We found that the rough surface results in shrinkage of the CO2 displacement path, slowing overall displacement rate. Additionally,the pinch-point effect in a rough nanochannel impedes the smooth progressionof the interface contact line, causing periodic velocity fluctuationthat further hinders CO2 displacement. We also simulatedthe CO2 displacement in rough nanoporous media, findingthat the rough surface leads to a substantial decrease in CO2 displacement efficiency, especially under low pressure gradientconditions. Our simulation results indicate that the rough surfaceof a shale nanometer pore has a nonnegligible effect on CO2 displacement.