【作者】 张铎远；

【导师】 步玉环；

【作者基本信息】 中国石油大学 ， 油气井工程， 2007， 硕士

【摘要】 在固井过程中,提高环空注水泥顶替效率是防止钻井液窜槽、保证水泥胶结质量和提高水泥环密封效果的基本前提。由于顶替效率的影响因素复杂多变,涉及到工艺措施、地层条件、井身结构、流体流动性能及固井工具等多个环节,难以利用室内实验手段进行精确物理模拟,因而利用数值模拟手段系统研究环空顶替机理具有重要的现实意义。本文基于大型CFD软件FLUENT,利用数值模拟的手段研究了浆体流变参数、偏心环空、“大肚子”及其它变量对顶替效率的影响规律。模拟结果表明:对于宾汉或幂律模式,增加水泥浆与钻井液的密度差、增加水泥浆的稠度系数或钻井液的流性指数、增加水泥浆的塑性粘度、以及增大水泥浆或钻井液的动切力,都有利于提高顶替效率;反之,增加水泥浆的流性指数或钻井液的稠度系数,或增加钻井液的塑性粘度,会使水泥浆的顶替效率降低。此外,顶替效率随着偏心度的增大而降低,迟流现象随偏心度的增加而趋于严重;对于“大肚子”井段,即使接触时间充分,也难以达到完全顶替,顶替效率的最低值在“大肚子”段与正常段交接处。研究结果有助于明确注水泥过程中环空顶替机理,为注水泥设计与施工提供必要的理论依据。更多还原

【Abstract】 In the course of cementing, improving the displacement efficiency incementingengineeringis abasicpremisetoprevent drillingfluidchanneling,guarantee the bonding strength of set cement and improve the sealingproperty of cement sheath. The displacement efficiency is affected by manyinteractedparameters, suchasthetechnologicmeasures,formationcondition,wellbore geometry, fluid mobility, cementing tools and so on. Due to thecomplexity of influencing factors, it is difficult to precisely simulate thedisplacement by means of laboratory experiments. It is, hence, of practicalimportance to systematical study the annular displacement mechanism bynumericalsimulation.Based on the large-scale CFD software FLUENT, the effects ofrheological parameters, eccentric annulus, special well condition and othervariables on the displacement efficiencywere studied bymeans of numericalsimulation.Thesimulationresults showthat increasingthedensitydifferencebetween the cement slurry and the drilling fluid, the consistency coefficientofcementslurryortheliquidityindex ofdrillingfluid,theplasticviscosityofcementslurry,andthe yieldpointofcementslurryordrillingfluid,allhelpto improve the displacement efficiency of cement slurry. On the contrary,increasing the liquidity index of cement slurry or the consistency coefficientof drilling fluid, or increasing the plastic viscosity of drilling fluid, willreduce the displacement efficiency of cement slurry. Meanwhile, when theeccentricity increases, the displacement efficiency decreases, and late-flowphenomenon becomes serious with the increase of eccentricity. For specialwell condition, if sufficient contact time is obtained, it is still hard to reachcomplete displacement. The lowest point of the displacement efficiency ofcement slurrylocates at the point which connects special well condition withnormal condition. Research results can contribute to better understand theannular displacement mechanism incement squeezing,and provide necessarytheoretical foundations for the design and execution of cementing.更多还原