Abstract: The deep burial and poor reservoir physical properties of Wei-42 block in Pucheng oilfield lead to the difficulty of waterflooding development, low recovery degree and poor development benefit. For this reason, nuclear magnetic resonance(NMR) and long core displacement experiments are carried out for high-pressure and low-permeability reservoirs with difficult water injection. On the basis of experimental research, CO_2 displacement scheme design optimization is carried out for Wei-42 block, and the reservoir numerical simulation model which can simulate artificial fracture is established, well spacing demonstration and parameter optimization are carried out. Six wells were selected and pilot test of CO_2 injection was carried out. The injection pressure was 17 MPa lower than that of water injection, which effectively supplemented formation energy and enhanced oil recovery by 15% on the basis of water flooding.