Abstract: Regarding the problems of difficult exploitation and high development cost in deeply buried heavy oil reservoirs with thin net pay, this paper integrates the advantages of VAPEX and proposes a new EOR technology for such reservoirs with injecting a low saturated vapor pressure polar organic gas PE. The viscosity reduction effect of this polar gas under two phases of gas and liquid were studied through phase observation experiments and viscosity measurement. Furthermore, its performance on viscosity reduction and oil displacement has been compared with LPG, which is commonly used in VAPEX. The research results indicate gaseous PE has good solubility in heavy oil and could dramatically reduces heavy oil viscosity. Liquid PE forms a low density and low viscosity phase by dissolving more and more bitumen in crude oil, which is better than the solution capability of LPG. The field pilot has shown that injection the organic polar gas can greatly increase the oil production of simulated well. The technology is practical and worthwhile large-scale implementation for deeply buried heavy oil reservoirs with poor qualities: thin net pay and low permeability.