Study of Supercritical State Characteristics of Miscible CO2 Used in the Flooding Process

Carbon dioxide flooding is a strategic replacement technology for greatly enhancing oil recovery in low-permeability oilfields, which includes social benefits resulting from carbon emission reduction and economic owing to the improvement of recovery. Therefore, it great significance develop apply CO2 storage petroleum industry. In reservoir conditions, usually under supercritical state, presenting both low viscosity high diffusivity gaseous state density liquid state. The special phase behavior directly affects its extraction capacity, change miscible between crude oil. this paper, ultra-high-pressure–high-temperature pressure–volume–temperature (PVT) system was used evaluate characteristics during process development. behaviors CO2/CH4/N2 were compared analyzed. Moreover, matching mechanism oil–gas miscibility investigated defined. This work deepened understanding flooding, providing theoretical guidance application injection on oilfields essential scientific basis implementation CCUS-EOR technology.