Study Of Steam Heat Transfer Law In Development Of Flue Gas Assisted SAGD

The heavy oil reserves are abundant,and its effective development has practical significance for alleviating the increasing energy demand.SAGD is an important technology for heavy oil development,but there are problems such as huge steam consumption,low heat utilization rate,and environmental pollution.Flue gas assisted SAGD technology has the dual significance of improving the SAGD performance and reducing greenhouse gas emission,which has a broad application prospect in the current situation of low oil price and green development.However,the research on the synergy between steam and flue gas is not enough,especially the understanding of how flue gas affects steam heat transfer in SAGD development,which limits the promotion and application of flue gas assisted SAGD technology.In this work,experiments including condensation heat transfer test,1D flow heat transfer test,and 2D visualization physical simulation were conducted to study the effect of flue gas on the heat transfer of steam in SAGD development and the related mechanisms.Firstly,considering the important influence of steam condensation on SAGD development,the condensation heat transfer experiment under the conditions of SAGD physical simulation was designed and carried out.It was found that after flue gas was added,the condensation pattern turned to film condensation,and the heat flux and the condensation heat transfer coefficient decreased,indicating flue gas can inhibit steam condensation and heat transfer.Secondly,1D flow heat transfer experiments were conducted using the sandpack with thermal-couples and heat-insulating layer.The results showed that due to the effect of flue gas,the temperature of front part of the sandpack slightly decreased by 1.57-4.39?,while the temperature of deep part significantly increased by 6.18-12.74?,suggeating the flue gas can expand the thermal sweep range of steam.Besides,the steam consumption in steam+flue gas experiment account for only 59.47% of that in pure steam experiment to reach the same heat level.On this basis,2D visualization model was used to simulate SAGD development and flue gas assisted SAGD development.The results showed that after the addition of flue gas,the steam chamber first grow upward then expand laterally with the temperature of steam chamber declining by 2-4?.Flue gas can make the sweep efficiency of steam chamber increase by 11.3%,the expansion angle increase by 10.07° and the height of steam chamber rise by 8.73%.Flue gas can not only inhibit the condensation heat transfer of steam on the way up,but also reduce the obstacle of the "countercurrent" of the crude oil and the condensate to the rising vapor,so more heat can be carried to the top of steam chamber,leading to the upward growth of steam chamber.Finally,the hypothesis that the injection of flue gas can promote the steam chamber to break through interlayer was proposed.Then its feasibility was proved by 2D visualization experiment.The results showed that flue gas not only can penetrate the interlayer and provide flow channel for subsequent steam,but also promote more heat to flow through the interlayer.By comparing the results of the experiments under different interlayer permeabilities,it is concluded the method is suitable for formation conditions where the permeability between the reservoir and the interlayer is not more than 30 under the experimental conditions.