The Honghe oilfield in Ordos Basin has difficulty achieving effective development due to low formation pressure

quick production decline and low recovery efficiency during natural depletion.In addition

natural fractures are well developed in Chang 8 tight sandstone reservoir

making it difficult to carry out waterflooding due to serious water channeling and low efficiency.Various CO

2

-EOR experiments including PVT

minimum miscible pressure and CO

2

flooding in fractured cores were performed to determine the feasibility of maintaining reservoir pressure via CO

2

injection.The performance of CO

2

puff-huff was also eveluated.The results show that the crude oil of Honghe oilfield swells significantly after CO

2

injection.The diffusion between crude oil and CO

2

gradually increased as the pressure grows.The measured miscible pressure of crude oil and CO

2

is 17.34 MPa

lower than the initial formation pressure of Honghe oilfield

indicating that miscible flooding of CO

2

is feasible.Multi-cycle CO

2

huff-puff experiments show that an additional oil recovery factor of 3.14% can be achieved on the basis of 4.04% of natural depletion.A comprehensive evaluation of the experiment results indicates that CO

2

injection is feasible in Chang 8 reservoir of Honghe oilfield.