Study On The Displacement Mechanism Of Thermal Fluid Flooding In Thin Layer Heavy Oil Reservoir

The injection of steam into thin layer heavy oil reservoir is difficult,and it has some problems,such as wasteful injection,large heat loss,low oil steam ratio and low displacement efficiency,so conventional development of such reservoirs by injection of steam is useless.Currently,steam,gas,viscosity agent and foaming agent are injected together into this kind of heavy oil reservoir,resulting in the formation of new technology called high temperature thermal fluid.In the process of injection of high temperature thermal fluid,gas can dissolve to cut down on oil viscosity and the heat loss,viscosity agent can strengthen the ability of viscosity reduction and promote steam injection,and foam has great effect of restraining steam channeling and extending the steam chamber.Making full use of the synergy effect of the various injection components can significantly improve development performance of thin heavy oil reservoir,but the mechanism of enhanced oil recovery by high temperature thermal fluid is unclear.Therefore,in this article,through the experiments of the interaction of flue gas and crude oil,the physical simulation of high temperature thermal fluid displacement and the experiments of high temperature foam profile control,the mechanism of high temperature thermal fluid to improve oil recovery has been analyzed and the roles of each component in high temperature thermal fluid have been verified.At first,this paper studied the influence of flue gas to heavy oil in the present of water and no water.The results show that the viscosity reduction rate of flue gas was 20% ~ 80%,and the higher water cut is,the smaller dissolved gas oil ratio is,and the worse effects of viscosity reduction is.Flue gas dissolved in the heavy oil can effectively reduce the interfacial tension of oil and gas,and the greater the pressure is,the higher dissolved gas oil ratio is,and the more obvious reduction effect is.On this basis,four displacement experiments of high temperature thermal fluid(steam flooding,flue gas assisted steam flooding,viscosity reducer assisted steam flooding and flue gas + viscosity reducer assisted steam flooding)were carried out to analyze flow law and oil displacement efficiency.Through comparing the effect of water-soluble viscosity agent and oil soluble viscosity agent on displacement pressure,it can find that water soluble viscosity agent HEOR-5 + steam has a high injection pressure,a low recovery efficiency and a poor displacement effect,and the flow resistance of water-soluble viscosity reducer agent HEOR-5 far outweigh the oil-soluble viscosity reducer agent DYR.Compared with steam flooding,the recovery of flue gas assisted steam flooding degree can be improved by 11%,and the recovery of flue gas + viscosity reducer assisted steam flooding can be improved by 16%.Finally,the experiments of high temperature foam plugging and profile control ability has been done,and the influencing factors of gas-liquid ratio,injection mode,crude oil,temperature and the range of foam permeability are analyzed.Results show that the sealing ability is strongest when gas liquid ratio is 1:1,and continuous injection is better than slug injection;and foam sealing effect is decline in the presence of oil,and with the increase of temperature the resistance factor decreases gradually.And when permeability differential is within the range of 0 to 6,high temperature nitrogen foam has a good capacity of shunt profile control,and high temperature nitrogen foam profile control ability becomes poor in the presence of oil.