Abstract:

It is reported in domestic and foreign literatures that higher displacement efficiency and oil recovery will be achieved
with gas injection by utilizing gravity in a tilt reservoir than in a reservoir with a little tilt. In this paper，by using numerical
simulation，the effects of dip angle and injecting position on CO2 displacement efficiency is studied. The result of the simulation
shows that with the increase of dip angle，recovery percentage by CO2 injection increases while the residual oil saturation in
the high part of the reservoir decreases. Furthermore，oil recoveries by injecting CO2 in the high part are higher than that in
the low part in all scenarios. And the larger dip angle，the better displacement effect can be obtained by injecting CO2 in the
high part as CO2 can form a small CO2 cap which is helpful for flooding oil. Experiments of the effect of different injection
scenarios with the practical geological model of large angle reservoir indicates that injecting CO2 in the high part can enhance
oil recovery by 8.69% more than injecting in the low part，and it activates more reserves. Preliminary success has been made
after the field application of injecting CO2 in the high part：half a year after injecting CO2 for，the central well in waist of the
reservoir restores from producing no liquid to producing 9.3 t oil.

Key words: dip angle, reservoir, CO2-flooding, EOR