The Numerical Study Of The Process For The Wellbore Sag Area Cementing Displacement Flowing And The Displacement Efficiency

In the process of oilfield development,the wellbore exist local sag,its root causes are inconsistent formation lithology and technical limitations caused by drilling the hole enlargement and sidewall erosion.The drilling fluid in the sag area is difficult to be replaced in the process of cementing displacement,the displacement efficiency of the cement slurry is low,eventually lead to poor cementing quality.Therefore,the study of the process for the wellbore sag area 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 wellbore sag area cementing displacement flowing is be simulated in computational fluid dynamics software Fluent.Respectively to study the flow pattern,density difference,the fluid properties,indentation length,angle of wellbore inclination,the annular clearance for the influence of the displacement efficiency of the cement slurry in the sag area,the simulation results show that using plug flow or turbulent flow displacement,increasing the density difference between the cement slurry and the drilling fluid,all help to improve the displacement efficiency of the cement slurry in the sag area.And optimal fluid properties which include viscosity,shear force,consistency coefficient and liquidity index of drilling fluid and cement slurry are found.The displacement efficiency of the cement slurry in the sag area is decreasing when annular size is reducing,or the indentation length is reducing,or angle of wellbore inclination is increasing.In addition,as the growth of the time,the displacement efficiency of the cement slurry in the sag area rose rapidly,when the displacement efficiency increases to a certain value after growth is slowing down,then the value no longer changes over time.The simulation results can contribute to improving the wellbore sag area 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 process of the wellbore sag area cementing displacement flowing,and provide necessary theoretical foundations for the design and execution of cementing.