Stimulation Mechanisms And Application Of Air Assisted Steam For Heavy Oil Reservoirs

Heavy oil reserves paly an important role in the world's petroleum supply.As the problems caused by steam injection are more serious during the late stage of thermal recovery process,it becomes an important issue to improve heavy oil recovery more efficiently.In this paper,the problems occurring during the air-assisted steam process for heavy oil recovery are studied on the basis of engineering thermodynamics,reservoir engineering,physical simulation and reservoir numerical simulation method.The thermophysical properties,including density,viscosity,specific heat capacity,enthalpy and thermal conductivity of saturated steam and air-steam system are calculated and compared according to the therotical formulas of engineering thermodynamics.A series of 2-D visualized experiments are performed with a 2-D visualized thermal recovery model,which visually present the areal sweep variation of oil layer after steam injection and air-steam injection,and illustrate the fluid migration in porous media both macroscopically and microscopically.Meanwhile,a 3-D thermal recovery facility is designed on the basis of similarity criteria.During the experiments,the temperature distribution and liquid production variation along the distance inner the 3-D model are monitored to analyze the mechanism of vertical sweep improvement by the injection of air-steam instead of steam alone.The fundamental physicochemical properties of heavy oil are identified by laboratory tests.Afterwards,the reaction between air and heavy oil under high temperature and high pressure are conducted.During the experiments,the variations of pressure,oil viscosity,tail gas composition and oil composition are recorded to reveal the oxidation characteristic between air and heavy oil under different conditions.Then,the influence of water content in oil,temperature,air-oil ratio and catalyst content on the reaction between air and heavy oil is explored and the important parameters of air injection technique are also optimized.Finally,the dynamic oil displacement characteristics and oil recovey of different displacement patterns are compared by conducting a set of sandpack experiments.Based on the geological property and production characteristic of a heavy oil block of Henan oilfield,the main cotrolling factors that influence the development effect of air assisted steam injecton for heavy oil are screened with numerical simulation method.Afterwards,the actual geological model is built and after history match,the injection and production parameters of air-assisted steam injection technique are optimized.