In order to solve a series of development contradictions such as water flooding and chan-neling in the middle and later stages of water injection development of Yanchang low porosity and low permeability reservoirs, through indoor CO2 and crude oil PVT phase experiments and slim tube ex-periments, variation characteristics of the phase behavior after CO2 injected into formation crude oil is studied as well as the minimum miscible pressure of CO2 and crude oil. The experimental results show that after CO2 injected into the crude oil, the saturation pressure gradually rises and the crude oil has a strong expansion capacity. At present, the volume expansion coefficient of the formation crude oil under the formation pressure is 1.2023, and the maximum decrease in the viscosity of the crude oil can reach more than 70％. The slim tube experiment shows that the minimum miscible pressure of CO2 and formation crude oil is 22.51 Mpa, and miscible flooding cannot be achieved un-der the original formation pressure. This study provides a theoretical basis for the feasibility of CO2 flooding in Yanchang Oilfield, and is of great significance to the long-term sustainable development of Yanchang low permeability reservoirs.
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