Volume 54

The effect of transitioning from water flooding to reduced-oxygen air flooding on oil recovery in low-permeability oil reservoirs LI Qihang, LI Yiqiang, YAN Zhiqian, WANG Wenxu, CAO Jinxin, ZHANG Yaqian, TANG Xuechen, SONG Tao, LIU Zheyu

Abstract

Reduced-oxygen air flooding can serve as an effective alternative for water injection in the development of low-permeability reservoirs. During the development process, there is a phenomenon of increased viscosity due to the mixture of crude oil oxidation and water. It is essential to clarify the impact of viscosity increase after crude oil-water mixture during low-temperature oxidation on oil recovery. This paper investigated the impact of water content on the viscosity increase of oil-water mixed fluids during air oxidation through static oxidation experiments. The results indicate that heavy components generated after crude oil oxidation can interact with water to form highly viscous fluids. As the water content increases from 0% to 70%, the viscosity of the mixed fluids initially increases and then decreases. It reaches its maximum value of 32.5 cp at a water content of 30%. The long core displacement experiment studied the impact of transitioning from water flooding to air flooding and nitrogen flooding on crude oil recovery under optimal viscosity conditions. Two sets of experiments, water flooding and gas flooding, were conducted for comparison. The results indicate that the highest oil recovery was achieved when transitioning from water flooding to air flooding. This suggests that the heavy components generated during crude oil oxidation in the air flooding process, along with the highly viscous fluid formed by interaction with water, can block high-permeability channels, exerting a localized profile modification effect. This leads to changes in gas flow channels and expands the effective gas sweep range. This leads to changes in gas flow channels and expands the effective gas sweep range.

Keywords reduced-oxygen air flooding,low-temperature oxidation(LTO),enhance oil recovery (EOR),heavy components