Under the situation of intensifying CO

2

emissions and increasingly serious environmental problems

carbon emission reduction is urgent. CO

2

-EOR is the main means of geological storage of CO

2

but most of the researches on CO

2

-EOR at home and abroad are to study the residual oil

and there are few studies on the form

of CO

2

storage during oil flooding. In this paper

nuclear magnetic resonance is used to detect CO

2

displacement online combined with numerical simulation is used to study the CO

2

storage morphology and distribution characteristics of different core saturated oil after gas flooding. The results show that the NMR technology combined with the microscopic gas flooding oil numerical simulation method can effectively study the microscopic storage morphology of CO

2

. When CO

2

in the core replaces crude oil

it first enters the large pore to drive oil

and after the pressure in the large pore reaches a certain level

the crude oil flows to the small hole throat with uneven distribution of capillary force around it

and the gas continues to drive the crude oil until the small pore pressure accumulates to a certain value in the small pore. Numerical simulations are performed using COMSOL Multiphysics software. Microscopic simulation results shows that CO

2

in large pores mainly exists in the form of continuous free gas

while CO

2

in small pores is first retained in dissolved form. There is no CO

2

completely stored in free gas or dissolved gas in both large and small pores.