Laboratory Study on the Oil Displacement Process in Low-Permeability Cores with Different Injection Fluids

Area of Science:

• Petroleum Engineering
• Reservoir Engineering
• Enhanced Oil Recovery

Background:

• Flooding technologies are crucial for low-permeability reservoir development.
• Mechanisms of oil recovery enhancement by different injection fluids require detailed investigation.
• Supercritical CO2 (ScCO2) injection is a promising EOR technique.

Purpose of the Study:

• To comparatively study supercritical CO2 (ScCO2), N2, and water injection in low-permeability tight cores.
• To reveal the effect of injection fluid physicochemical properties on oil recovery efficiency.
• To understand the mechanisms behind enhanced oil recovery in unconventional reservoirs.

Main Methods:

• Flooding experiments were conducted using Berea sandstones of varying permeability and kerosene.
• Quantitative comparisons of oil recovery factor and displacement pressure difference were performed.
• System pressures of 15 MPa and 25 MPa were utilized.
• Interfacial tension (IFT) measurements were conducted.

Main Results:

• ScCO2 injection achieved significantly higher oil recovery efficiencies (59-91% at 15 MPa, 84-92% at 25 MPa) compared to N2 (26-40%, 21-52%) and water (43-46%, 45-49%).
• Miscibility conditions were achieved between ScCO2 and oil, leading to superior recovery.
• ScCO2 and N2 exhibited lower displacement pressure differences (approx. 10 MPa/m) than water flooding (approx. 100 MPa/m).

Conclusions:

• Supercritical CO2 injection demonstrates substantial advantages for enhancing oil recovery in low-permeability and unconventional reservoirs.
• The miscibility of ScCO2 with oil is a key factor for its high recovery efficiency.
• This research provides insights into CO2 flooding mechanisms and guides its utilization in oilfield development.