Experimental study on gas EOR for heavy oil in glutenite reservoirs after water flooding

摘要

Glutenite reservoirs retain large quantities of residual oil after water flooding. Gas EOR has proven to be an efficient and environmentally friendly method to improve recovery ratios in conventional reservoirs. However, similar experiments carried out on glutenite reservoirs are rare in the literature. Based on PVT analysis, this paper investigates the potential of 4 gas agents (CO2, associated gas, flue gas and deoxygenated air) in the tertiary recovery process. The results show that due to the strong inhomogeneity of glutenite formations, water flooding produces poor recovery ratios, as evidenced by the large amount of oil remained in cores. In the gas EOR stage, in glutenite formations, the WAG strategy is less efficient than the continuous injection approach, which differs from the conventional pattern. Associated gas achieves the greatest increase in oil recovery in the continuous injection mode, with CO2 being the most effective gas agent in the WAG mode. Flue gas and deoxygenated air are more suitable for the huff and puff mode from an economic perspective. Tests also demonstrate that an earlier transition to gas displacement produces more favorable results.