Addressing the challenges of moderate to strong velocity sensitivity damage and strong to extremely strong water sensitivity damage in the medium and deep heavy oil reservoirs of Xinjiang oilfields

which lead to suboptimal waterflooding outcomes

a study was conducted leveraging the unique physical and chemical properties of CO

2

. Utilizing high-temperature

high-pressure PVT apparatus and long core displacement equipment

the feasibility of enhancing oil recovery through CO

2

flooding/huff and puff was explored by determining the high-pressure physical properties of CO

2

-crude oil and analyzing the composition and viscosity changes of the produced oil with gas chromatography and high-temperature

high-pressure rheometry. The experimental results show that 57.345% mole fraction of CO

2

can increase the dissolved gas-oil ratio（GOR） from 32 m

3

/m

3

to 149.3 m

3

/m

3

the bubble point pressure（

p

b

） from 6.8 MPa to 15.7 MPa

the volume coefficient of crude oil from 1.06 to 1.27

the density of crude oil from 0.896 5 g/cm

3

to 0.854 8 g/cm

3

and the viscosity of crude oil from 419.3 mPa·s to 253.4 mPa·s. Therefore

CO

2

can effectively supplement the formation energy

increase the elastic energy of crude oil and reduce the seepage resistance. The first round of 0.95 PV（pore volume） CO

2

flooding has a crude oil recovery of 32.8%

and the fluid in the porous medium is redistributed after 24 hours of shut-in. The second round of 0.5 PV CO

2

flooding can increase the crude oil recovery by 17.9%. The crude oil recovery of five rounds of CO

2

huff and puff is 63.5%. The viscosity of the produced oil tends to decrease

mainly due to the deposition of asphaltenes in crude oil in porous media. The experimental results have confirmed the feasibility of CO

2

flooding/huff and puff in the recovery of heavy oil in the middle and deep layers of Xinjiang Oilfield.