The Mechanism And Application Of Thermal-chemical Steam Flooding In Shallow And Thin Heavy Oil Reservoirs

The reserve of heavy oil around the world is so large that the development of heavy oil reservoirs has been gradually emphasized.Nevertheless,due to heat losses,steam overlapping,steam channeling and other serious problems,the efficiency of conventional thermal recovery methods reduces,so it is an urgent requirement for technology that enhances oil recovery.In this paper,according to the theoretical basis of reservoir physics,seepage mechanics,reservoir engineering,various research methods are used,such as physical simulation,reservoir engineering calculation and numerical simulation.The mechanism and application of thermal-chemical steam flooding in heavy oil reservoirs are deeply studied.Physical properties for different types of heavy oil have been determined though the laboratory experiment.On this basis,evaluations and selections of the commonly thermal chemical flooding agents(viscosity reducers and foaming agents)used for heavy oil reservoir are finished.Viscosity and interfacial tension were assessed under different temperatures,Based on the evaluations of the static properties,dynamic properties,the salt resistance and oil resistance of the different foaming agent,we ultimately selected the optimal agents for thermal chemical flooding in heavy oil.With a visualization device which can be used to simulate thermal recovery process for different fluid injection patterns,the microscopic sweep efficiency and displacement efficiency are observed and analyzed.The optimal composite system is determined.Meanwhile,the movement of emulsion droplets in porous media is determined.In addition,microscopic characteristics of the thermal foam,such as migration,deformation,fracture,fusion and regeneration are observed.The mechanism of plugging channellings and inproving the sweep efficiency is summarized.Considering characteristics of reservoir heterogeneity and steam channeling,based on the moving range of crude oil,using reservoir engineering and numerical simulation methods,in combination with actual oilfield development well group,the comparison and analysis of the flooding conversion efficiency are made among the inverted five-spot well pattern,the inverted seven-spot well pattern,the inverted nine-spot well pattern,the inverted nine-spot vacuated well pattern and small homocentric squares shaped well pattern.It is suggest that small homocentric squares shaped well pattern is optimal.Based on the above optimal composite system and the optimum well pattern,according to the actual geological parameters of layer IV9 in Biqian-10 shallow and thin heavy oil reservoir in Gucheng oilfield,geologic model is firstly built.Then,the optimization of development mode,steam injection intensity and production-injection ratio are made by the method of numerical simulation.Moreover,we present the plan and prediction.In this paper,the research results improve the development theory of synergistic mechanisms of the thermal chemical flooding.It is of great significance for guiding the extended application of the technology in heavy oil reservoir.