CO2-assisted EOR technologies appear to be low-cost and eco-friendly means to boost crude oil production of dense reservoirs. The potential of CO2 huff-n-puff process and CO2 flooding processes have been extensively investigated in tight sandstone reservoirs, while few work has been done in tight conglomerate reservoirs, which exhibit strong micro-heterogeneity. In the present work, we quantitatively investigated the potential of CO2 injection processes in tight conglomerate reservoirs under reservoir conditions (formation pressure 23 MPa, temperature 69 degrees C). High temperature and high pressure nuclear magnetic resonance (NMR) online monitoring system was used to pore-scale monitoring the change of oil saturation in-situ through NMR T-2 spectrum, one-dimensional (1D) NMR spatial distribution of signal and two-dimensional (2D) NMR images. It was demonstrated that CO2 injection processes were applicable in target tight conglomerate reservoir with recovery factors of about 35%. The results of this study pore-scale revealed the feasibility of CO2-assisted EOR technologies in tight conglomerate reservoirs. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.