Study On Balanced-steam-injection Technique On Dual-Horizontal-Well SAGD By Multistage-steam-injection String Combination

The SAGD technology of double horizontal wells has the advantages of low accumulative steam-oil ratio and high recovery rate,which is the frontier technology of heavy oil development.However,there are still problems of steam channeling,heel-toed effect and uneven steam absorption along the SAGD,which seriously affects the mining effect of the SAGD.As a result,the balanced steam injection technology along the horizontal well has become the key research content to further improve the SAGD development effect.Based on the influence factors of double horizontal SAGD,this paper analyzes the main control factors of geological influencing factors and development influencing factors by orthogonal experimental design method.It is found that the heterogeneity of formation and the size of steam injection string have great influence on steam absorption.Therefore,the section design method is proposed for the influence of formation heterogeneity,and the multistage pipe string combined steam injection is proposed for the influence of pipe string size.Firstly,the mathematical model of multistage pipe string combined with mass conservation equation,energy conservation equation and momentum conservation equation is established by combining Venturi equation and Bernoulli equation.Then,The model is solved and calculated by numerical method.Based on the model of CMG flexible well,the accuracy and reliability of the model are verified and the steam injection effect of multistage string combination is compared and analyzed.Secondly,the structure of the steam flow device introduced in the subsection design is optimized,and a mathematical model is established to solve the distribution structure of the nozzle along the path.And the FCD model is used to verify it,and then the steam injection effect of steam flow device is compared and analyzed.Finally,the research results of multistage pipe string combined with steam injection and steam flow control device are applied to the GH71 well of Liaohe Oilfield.Five kinds of balanced steam injection processes are designed.The steam injection effect and mining effect of these five processes are predicted by using reservoir numerical simulation software.