关键词: 致密油藏, 　最小混相压力, 　CO2驱油, 　界面张力

Abstract: The minimum miscible pressure is one of the important parameters of CO2 injection in oil field. In order to determine the minimum miscible pressure between crude oil and CO2 in the tight reservoir of lucaogou formation, jimusar sag, Xinjiang, the laboratory slim tube test and interfacial tension test were carried out. The results show that the MMP measured by slim tube test in Xinjiang tight oil reservoir is 18.70 MPa, slightly higher than the MMP measured by the interfacial tension experiment, which is 18.44 MPa. The difference between the two is 1.4%, and both lower than the reservoir pressure of 43.00 MPa. Therefore, CO2 and crude oil can be miscible under the reservoir conditions. When the equilibrium pressure increases, the IFT decreased more as more CO2 dissolved in crude oil. When the system equilibrium pressure increased from 0.73 MPa to 28.46 MPa, the IFT value between crude oil and CO2 decreased from 22.62 mJ/m2 to 1.83 mJ/m2. When the equilibrium pressure was between 0.73 MPa to 13.33 MPa, the dissolution of CO2 in crude oil took the leading role. However, when the equilibrium pressure was between 15.84 MPa to 28.46 MPa, the extraction of light components in crude oil took the leading role, and the interaction mechanism between crude oil and CO2 changes from CO2 solubility to CO2 extraction of light components at the pressure of 13.67 MPa. Through the experimental study, the understanding of the MMP of the target reservoir and the microscopic interaction mechanism between crude oil and CO2 is deepened, which provided theoretical support for the formulation of CO2 injection development of the target reservoir.

Key words: Tight oil reservoir, Minimum miscible pressure, CO2 flooding, Interfacial tension