The Numerical Study Of The Hollow Wellbore Cementing Displacement Efficiency

In the process of oilfield development,due to the inconsistent lithology and drilling technology and other factors often cause local hole enlargement and sidewall erosion,forming locally hollow wellbore,the site is called “expanding well”,which not only brings challenge to drilling,but also to the cementing quality put forward higher requirements.In order to achieve the good effect of downhole packer,obtain a relatively high cementing quality,it is necessary to improve the displacement efficiency of the cement slurry in the cementing process,therefore,the study of the process for the hollow wellbore cementing displacement flowing and the displacement efficiency to improve the cementing quality and efficiency has important significance.Based on the non-Newtonian fluid mechanics basic theory and basic control equation of fluid motion,combined with the knowledge of the cementing displacement theory,the process of the hollow wellbore cementing displacement flowing is be simulated in CFD software Fluent.Respectively to study the flow pattern,hole enlargement section length,density difference,the fluid properties for the influence of the displacement efficiency of the cement slurry in the hollow part,the simulation results show that the flow pattern,hole enlargement section length,density difference are more important than fluid properties to the displacement efficiency;using plug flow or turbulent flow displacement,increasing the density difference between the cement slurry and the drilling fluid,the consistency coefficient of cement slurry or the liquidity index of drilling fluid,the yield point of cement slurry or drilling fluid,and the plastic viscosity of cement slurry(controlled to about 0.05Pa·s),all help to improve the displacement efficiency of the cement slurry in the hollow part,on the contrary,the displacement efficiency of the cement slurry in the hollow part will be reduced.In addition,the displacement efficiency of the cement slurry in the hollow part increases constantly with the extension of time,when the displacement efficiency increases to a certain extent,the displacement efficiency of the cement slurry in the hollow part is essentially the same.The simulation results can contribute to improving the hollow wellbore cementing displacement efficiency and cementing quality and is significant,at the same time,the research results can contribute to better understand the displacement mechanism in the the process of the hollow wellbore cementing displacement flowing,and provide necessary theoretical foundations for the design and execution of cementing.