New Understanding of the Retention Mechanism of “Residual Oil in the Form of Oil Droplets (or Oil Column)”

Abstract

Abstract Based on the oil-water two-phase liquid flow model, with equal-viscosity and water-wet unequal-diameter parallel channels, the previous researches on the retention mechanism of “residual oil in the form of oil droplets or oil column” during water flooding, and they stated that “residual oil in the form of oil droplets (or oil column)”can be retained in both large and small channels. Re-examination of the model shows that “residual oil in the form of oil droplets (or oil column)” cannot be retained in large channels, but only in small channels. By changing the wettability and oil-water viscosity (variable viscosity) of this model, the small channel retention characteristics of “residual oil in the form of oil droplets (or oil column)” remain unchanged. This research shows that: (1) When the oil-water phase flows in the unequal-diameter parallel channel model, the flow velocity of the large channel is always greater than the small channel, and the “residual oil in the form of oil droplets (or oil column)” is always retained in the small channel. (2) The retention of small channels of “residual oil in the form of oil droplets (or oil column)” is general, and is not affected by changes in factors such as pressure difference, capillary force, total flow, wettability, and oil-water viscosity ratio.