Mechanisms of asphaltene deposition and formation damage during CO2 flooding at the reservoir scale

During CO2 flooding in deep reservoirs, changes in reservoir fluid properties may induce asphaltene precipitation and deposition, leading to porosity–permeability impairment. While most previous studies rely on core-scale experiments or digital rock simulations, reservoir-scale investigations of deposition distribution and associated damage remain limited. In this work, a reservoir-scale CO2 flooding model coupled with asphaltene deposition was developed using actual temperature–pressure conditions and calibrated fluid properties from a deep reservoir. The model was validated against the analytical solution of infinite-acting radial flow. The effects of reservoir heterogeneity, CO2 mole fraction, injection rate, formation permeability, and well pattern on CO2 storage, deposition rate, and porosity–permeability damage were systematically analyzed. Results show that increasing the CO2 mole fraction from 0.2 to 0.8 increases the deposition rate by 19.56%, accompanied by porosity and permeability damage increments of 29.69% and 46.91%, respectively. Increasing the injection rate from 2 × 104 to 8 × 104 m3/day reduces the deposition rate by 16.83% and significantly mitigates formation damage. Higher formation permeability also suppresses deposition and associated impairment. The inverted nine-spot well pattern provides the highest CO2 storage and the lowest damage. Gray relational analysis indicates that formation permeability most strongly controls deposition rate, whereas well pattern dominates storage efficiency and formation impairment. These results clarify the coupled mechanisms of CO2 storage and asphaltene-induced damage in deep reservoirs.