Characteristics and mechanisms of supercritical CO2 flooding under different factors in low-permeability reservoirs

Abstract

In recent years, supercritical CO2 flooding has become an effective method for developing low-permeability reservoirs. In supercritical CO2 flooding different factors influence the mechanism of its displacement process for oil recovery. Asynchronous injection–production modes can use supercritical CO2 to enhance oil recovery but may also worsen the injection capacity. Cores with high permeability have higher oil recovery rates and better injection capacity, however, gas channeling occurs. Supercritical CO2 flooding has a higher oil recovery at high pressure levels, which delays the occurrence of gas channeling. Conversely, gas injection has lower displacement efficiency but better injection capacity at the high water cut stage. This study analyzes the displacement characteristics of supercritical CO2 flooding with a series of experiments under different injection and production parameters. Experimental results show that the gas breakthrough stage has the fastest oil production and the supercritical CO2 injection capacity variation tendency is closely related to the gas–oil ratio. Further experiments show that higher injection rates represent significant ultimate oil recovery and injection index, providing a good reference for developing low-permeability reservoirs.