Visualization and Measurement of CO₂ Flooding in Porous Media Using MRI

Abstract

CO2 flooding is used extensively as a commercial process for enhanced oil recovery. In this study, the visualization of CO2 flooding in immiscible and miscible displacements in a high-pressure condition was studied using a 400 MHz MRI system. For CO2 immiscible displacement, the phenomenon of CO2 channelling or fingering was obviously due to the difference in fluid viscosities and densities. Thus, the sweep efficiency was small, and the final residual oil saturation was 37.2%. For CO2 miscible displacement, the results showed that pistonlike displacement occurred, and the phenomenon of the miscible regions and CO2 front was obvious. The viscous fingering and gravity override caused by the low viscosity and density of the gas were restrained effectively, and the velocity of the CO2 front was uniform. The sweep efficiency was high, and the final residual oil saturation was 13.5%, indicating that CO2 miscible displacement could recover more oil compared with CO2 immiscible displacement. Finally, the average velocity of the CO2 front was evaluated by analyzing the oil saturation profile. A special core analysis method was applied to in situ oil saturation data to directly evaluate the effect of viscosity, buoyancy, and capillary pressure on CO2 miscible displacement.

Magnetic resonance imaging analysis on the in-situ mixing zone of CO2 miscible displacement flows in porous media

“…Zhao et al 31,32 proposed an equation for calculating the averaged in-situ CO 2 miscible displacements in porous media using MRI. Zhu et al 15 measured the averaged in-situ mixing zone velocity using Zhao's equation at near-miscible displacements conditions using MRI.…”

Microscopic pore structure of Chang 63 reservoir in Huaqing oilfield, Ordos Basin, China and its effect on water flooding characteristics

“…The water-free stage in the water flooding process of type I pore structure is relatively short, but the ultimate oil displacement efficiency is still relatively high, with the ultimate-stage displacement efficiency range of 37.1-42% (averaging 39.03%). Among all the four types of pore structures, type I pore structure is of the highest ultimate-stage displacement efficiency (Zhao et al 2011). …”

Simulation and visualization of the displacement between CO2 and formation fluids at pore-scale levels and its application to the recovery of shale gas

“…4 Local phase velocities of a CO 2 and b oil. (Zhao et al 2011b) flow during the displacement process, and quantitative information about the interfacial areas and fluid saturations was not acquired. The study of Zhang et al (2011b) was the first to quantitatively evaluate the influence of the capillary forces and porous media heterogeneity on the liquid CO 2 -water displacement in a dual-permeability pore network micromodel using fluorescence microscopy.…”