Experimental simulation study on displacement efficiency of heavy oil in shallow reservoir by hot water and carbon dioxide

The shallow heavy oil reservoirs of Qigu group in the Nine-six District of Xinjiang Oilfield have entered the late stage of steam mining. The exploitation of this heavy oil reservoir has experienced steam stimulation, encryption adjustment and steam flooding. The oil recovery factor was 37%. At present, the effect of single steam flooding has obviously decreased, along with serious formation deficit, low steam heat utilization efficiency, uneven gas inhaling, variant sweeping ability, large oil-water mobility ratio, and low oil recovery. Hot water combined CO₂ flooding is an effective way to enhance oil recovery by making full use of hot water heating effect and huge CO₂ dissolve in crude oil leading to viscosity reduction. In this paper, series of simulated flooding experiment of Nine-six district heavy oil by hot water and CO₂ in different injection ways including hot water flooding, hot water and CO₂ simultaneous injection, hot water and CO₂ slug injection were researched. The results show that the cumulative displacement efficiency(ED)of hot water flooding is 49.19%, the maximum cumulative ED of hot water and CO₂ simultaneous injection is 71.25%, and the maximum cumulative ED by hot water and CO₂ slug injection is 85.96%. The change of four-component of the produced oil and the residual oil in the core was analyzed.