Simulated Experimental Studies On Steam-CO₂ Combination Flooding For Heavy Oil Reservoir Development

Heavy oil is an unconventional resources, which is of great significance to relieve the tension supply of energy. Steam-CO₂ combination flooding can not only enhance oil recovery, but also reduce the emission of CO₂, which is dramatically meaningful to global warming and environmental protection. The solution properties of CO₂ in heavy oil and heavy oil-water system was investigated, and the factors that influence the solution was analysed by self-made device. The viscosity of heavy oil, heavy oil-water system, heavy oil-CO₂ system and heavy oil-water-CO₂ system were measured by high pressure and high temperature falling sphere viscometer, and the influencing factors such as temperature, pressure, solubility and water ratio were also studied. A series of simulated experiments include steam flooding, steam-CO₂ combination flooding and steam-N2 combination flooding were studied by a lot of sand pack models and the flowing mechanisms apparatus of heavy oil. In addition, the injection parameters which impact oil recovery such as injection temperature, injection rate, CO₂ injection time, CO₂ injection rates was optimized. Stimulation mechanism of steam-CO₂ combination flooding is analysed as well.Experimental results show that the bubble-point pressure of heavy oil and heavy oil-water systems increase with temperature rise and water ratio decline. Solubility of CO₂ in heavy oil and heavy oil-water systems is smaller than that in thin oil, and reduces with temperature rise, water ratio rise and saturation pressure decline. The viscosity of heavy oil and heavy oil-water system decreases up to 99% dissolved by CO₂. Steam flooding can enhance water flooding recovery and reduce water ratio for heavy oil reservoir. As the increasing of injection rate and injection temperature, water ratio of produced fluid decreases and recovery increases. Compared with steam flooding, recovery of steam-CO₂ combination flooding improves up to 30%, and water ratio of produced fluid decreases up to 30%. Solution of CO₂ had demulsification of heavy oil-water systems, reduces viscosity of heavy oil effectively, improves utilization of steam, increases swept volume and enhances oil recovery.